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286 Cards in this Set
- Front
- Back
sin 0, 30, 45, 60, 90, 180
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0, 1/2, sqrt2/2, sqrt3/2, 1, 0
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cos 0, 30, 45, 60, 90, 180
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1, sqrt 3 /2, sqrt2/2, 1/2, 0, 1
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one angstrom
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10^-10 m
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1 eV
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1.6 E-19 J, the energy acquired by an e- accelerating thru 1 V
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giga
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G/B = 10^9
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pico
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p = 10^-12
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torque
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rF sin(theta) = r cross F, negative is cw and positive is ccw
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translational motion equations
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v = v(o) + at, x = v(o) t + 1/2at^2, v^2 = v(o)^2 + 2ax,
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centripetal acceleration
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v^2 / r
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work
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Fd cos(theta) = F dot d = change in KE
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efficiency
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work out / work in = load x load dist / effort x effort d
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momentum
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mv
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impulse
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J = Ft = change in momentum
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power
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work / time, and 1 Watt = 1 J/s
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potential energy of a spring
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U = 1/2 k x^2
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center of mass
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com = sum of m(i)x(i) / sum of m(i)
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center of gravity
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sum of weight(i)x(i) / sum of weight(i) where w=mg
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average force of impact
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mass x average acceleration, where <a> = delta v / delta t... so if you increase the collision time, you decrease the force of impact ; also impact force = change in momentum / time
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joule
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1 N *m
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energy lost to heat due to friction
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equals work done by friction
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absolute zero
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0K, -273 C, -460 F
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freezing and boiling of water
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freezing: 273 K, 0 C, 32 F boiling: 373 K, 100 C, 212 F
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celsius to farenheit
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Tf = (9/5)Tc + 32
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temperature measures...
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the average random KE of the molecules of a substance (NOT the total KE)
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thermal expansion, length
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change in L = alpha * L * (change in T) where alpha is the coefficient of linear expansion
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percent change in length or volume
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change in L / L or change in V / V
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thermal expansion, volume
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change in V = beta * V * change in T where beta = 3 *alpha
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conduction
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heat transfer thru collisions
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convection
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heat transfer thru mass motion of heated material, e.g. plumes of smoke
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radiation
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heat transfer via electromagnetic waves
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1 Cal
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is 10^3 calories = 3.97 Btu = 4184 J
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heat gained or lost during a temperature change
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Q = m*c*change in T (if Q>0, heat is gained), where c = specific heat
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specific heat
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heat required to raise the temperature 1K or 1C of 1 kg of a substance
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heat of transformation
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L = heat gained or lost during a phase change, Q = mL, can be heat of fusion or vaporization
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pressure
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is (normal) force per unit area, F/A, tmeasured in Pa or atm
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1 pascal
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N/m^2
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1 atm
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the pressure at sea level = 1.1013 E5 Pa
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change in internal energy of a system
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delta U = Q - W, heat transferred to system - work done by system
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work done by a system, isobaric
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W = P*change in V (isobaric = constant P)
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adiabatic
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no heat transfer, Q = 0 so change in U = -W
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if volume is constant?
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no work is done by the system, W=0 so change in U = Q
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if a closed cycle?
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no change in internal energy, so U=0 and Q=W
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isothermal
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constant temperature
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for a reversible isothermal process, what is the change in entropy?
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delta S = Q/T
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in an isolated system, change of entropy?
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can never decrease (energy must be put into a system for entropy to decrease), but it will increase if the rxn is irreversible. No change if rxn is reversible.
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density
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p = m/V ; measure in kg/m^3
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density of water
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10^3 kg/m^3 or 1 g/cm^3
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weight from density?
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weight = mg = pVg (mass = density * volume)
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specific gravity
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the ratio of density to water density (10^3)
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the absolute pressure in a fluid due to gravity
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P = Po + pgh where Po = surface pressure
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gauge pressure
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Pg = absolute pressure - P(atm)
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Pascal's principle
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pressure is transmitted to every portion of a closed, incompressible fluid, so change in pressure = F1/A1 = F2/A2 and a displacement of volume in one area must equal the displacement in another (V = A1d1 = A2d2)
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Archimede's principle
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a body is buoyed up in fluid by a force equal to the weight of the fluid that it displaces; so the object will float as long as weight of displace fluid > object weight
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adhesion
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attractive force between liquid and molecules of another substance
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cohesion
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attractive force between molecules of same substance; causes surface tension because liquid have a net force pulling them down
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mass of a fluid flowing through a x-sectional area per second?
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area*velocity*density = constant
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is flow faster or slower through narrower passages?
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faster: v1A1 = v2A2 = constant
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Bernoulli's equation
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energy is conserved as fluid flows: P1 + (pv1^2)/2 + pgy1 = the same for 2 = constant; NOTE: if y1 = y2, then pressure decreases as velocity increases.
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viscosity
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the internal friction of a fluid; gas is less viscous than liquid because it is less dense. "nu" is measured in units of N*s/m^2 or dyne*2/cm^2 = poise and 10 poise = 1 N*s/m^2
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laminar flow
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thin layers of liquid sliding over one another
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laminar vs. turbulent flow?
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for fluid flowing through a tube of diameter D, velocity above a critical value, v(c), turns to turbulent flow: v(c) = (N*nu)/pD where N is Reynolds number and n is viscosity
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Young's modulus
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Y = (F/A) / (delta L / L) = stress/strain ; a large Y indicates a large stress produces only a small strain = a strong material
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stress vs. strain
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stress is the force pwer unit area where F is perpendicular to the area (i.e. pressure), and strain is the elongation per unit length (delta L / L)
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moduli
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different quantities that describe elasticity of a solid
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yield strength
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the point beyond which a material does not return to its original dimensions
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Shear modulus
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S = (F/A) / (x/h), describes shearing = a deforming stress where force is parallel to area
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Bulk modulus
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B = delta P / (delta V / V)
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electrostatic force
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the force between stationary charges
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charge of an electron
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1.60 E -19 C (the fundamental unit of charge)
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Coulomb's law
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force = k *q1*q2 / r^2 (magnitude of electrostatic force)
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electrostatic constant
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or Coulomb's constant, k = 8.99 E9 N*m^2/C^2 = 1/(4*pi*epsilon(o))
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permittivity of free space
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epsilon(o) = 8.85 E-12 C^2/N*m^2
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doubling the distance between two charges, changes the force?
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reduces the electrostatic force by 1/4, F is proportional to 1/r^2
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Electric field
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E=F/q in units of N/C = V/m, and where q is a positive test charge
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direction of an electric field
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toward negative, away from positive (therefore a negative charge feels a force opposite the field)
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electric potential at a point
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is the amount of work needed to move a positive charge from infinity to that point divided by the test charge: V = W/q in units of Volt = J/C
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1 V
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J/C
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electric potential of a point charge
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V = kq/r at a distance r from the point charge q
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potential difference
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V(b) - V(a) = W(ab) / q(o)
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electric potential across a cell membrane
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70-90 mV
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approximate pulse voltage of a pacemaker
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10 V
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electric potential energy
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U = qV = W (needed to move q from inifinity to that point)
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potential (at point P) of an electric dipole
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V = kq (1/r(1) - 1/r(2)) = sum of the two potentials
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potential at a large distance from a dipole?
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r(1)r(2) is approximately r^2 and r(2) - r(1) = d cos(theta) where theta is the angle between d and r (r is drawn at the midpoint, 1/2d)... so V = kqd * cos(theta) * 1/r^2
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dipole moment
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p = qd with units C*m and direction from negative to positive charges
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perpendicular bisector of a dipole
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when theta = 90, V =0 and the electric field along the line is E = kp / r^3 , and the field points opposite to p
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a dipole in a uniform external electric field
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experiences a torque, T = Fd*sin(theta) = qEd sin(theta) = pE*sin(theta) where E is the external electric field and theta is the angle between p and E
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during an isothermal process, how are P and V related?
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as P increases, V will decrease and vice versa
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if volume of a gas is constant, does gas do work?
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no, and delta T = PV/nR (from ideal gas law)
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units of magnetic field
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Tesla = N*s/m*C = 10^4 Gauss
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magnetic force
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F = qv cross B = qvB*sin(theta) where theta is the angle between qv and B
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right hand rule for magnetic force
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thumb in direction of q*v, fingers point in direction of B, and palm is in direction of magnetic force
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cross vector unit
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into the page
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work done by a magnetic force
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zero, because it is always perpendicular to velocity and the magnetic field
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a charge moving perpendicular to the magnetic field
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results in a circular motion with constant speed in the plane perpendicular to B
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radius of a charge in circular motion due to B
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r = mv/qB
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electric current
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flow of charge, I = delta q / delta t, with units of ampere
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1 A
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1 C/s
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direction of electric current
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from high to low potential, i.e. the direction of positive charge (opposite the actual flow of electrons from low to high potential)
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force on a current-carrying wire
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F = I*LBsin(theta) where L is the length of the wire, and theta is the angle between B and the wire (use RHR for direction)
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ferromagnetic
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e.g. Fe, Ni, and Co
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Curie Temperature
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temperature above which ferromagnetic material become paramagnetic; if Curie T is above room temp, the material is permanently magnetized
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direction of magnetic field lines
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from north to south poles (note that our north pole is actually a magnetic south pole)
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magnetic field due to an infinitely long straight wire
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at a perpendicular distance r, B = nu(o)*I / (2*pi*r), direction uses RHR (thumb in direction of current, and fingers curl around wire)
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permeability of free space
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nu(o) = 4*pi E-7 T*m/A = 1.26 E-6 T*m/A
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magnetic field at the center of a circular loop
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B = nu(o)*I / 2*r , magnetic field lines point into the page on one side and out on the other of the loop
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DC vs AC
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direct vs alternating current
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electromotive force
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emf = epsilon = voltage across the terminals of a cell when no current is flowing
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actual voltage supplied by a cell
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V = emf - I*R(internal)
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Ohm's Law
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voltage drop across a resistor is proportional to the current it carries, V = I*R
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units of resistance
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ohm
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resistance of a conductor
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inreases with increased length, decreased cross-sectional area
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resistivity
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the intrinsic resistance to current flow of a material, p, where R = p*L/A
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resistance and temperature
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are proportional in most materials, except glass, pure silicon, and most semiconductors
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power dissipated by a resistor
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P = I*V where V is the potential across the resistor, = I^2 *R = V^2/R
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Kirchhoff's Laws
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junction rule (currents in = out, due to conservation of electric charge) and loop rule (energy is conserved in complete loop)
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resistance, series vs. parallel
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adds in series, 1/R(parallel) = 1/R(1) +1/R(2) ... because parallel arrangment increases the cross sectional area of a conductor, i.e. increases the paths by which current can flow
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voltage across parallel resistors
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each have same voltage drop
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when n identical resistors are wired in parallel, R =
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R(parallel) = R/n
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STP
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standard temperature and pressure (for gases), 273 K and 1 atm
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an ideal gas
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a gas that experiences no intermolecular forces and whose particles occupy no volume
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conditions under which gases behave like ideal gases
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low pressures, high temperatures
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Ideal Gas Law
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PV = nRT
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ideal gas constant
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R = 8.31 J/K*mol
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effect of changing T on internal energy of a monoatomic ideal gas
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delta U = 3/2 * nR * deltaT
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an ideal gas and internal energy
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internal energy is completely dependent on temperature; so if no deltaT, no deltaU
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sign of Q for heat added to a system
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Q>0 , positive
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sign of W for work done by the gas
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W>0, positive when the gas loses energy; if work is done ON the gas, then W is negative
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change in internal energy for a gas
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deltaU = Q - W
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work done by a gas during a thermodynamic process
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equal to the area enclosed by its P-V curve
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decreased volume due to...
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work done ON the gas, therefore area under P-V curve is a negative quantity
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cyclic processes
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no change in internal energy, but work done by gas = enclosed area
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for an isothermal process, internal energy...
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does not change (for an ideal gas) and Q = W; also P and V are inversely related
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temperature change if volume increases at constant P
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T increases
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capacitor
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stores charge
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capacitance
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C = Q/V where Q is the charge on one plage and V is the potential difference, in units of farads; dependent on the geometry of the two conducting surfaces
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1 F
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C/V = also the charge on a mole of elementary charges = 9.65 E4 C
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capacitance of a parallel plate capacitor
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C = epsilon(o)*A/d where A is the area of overlap of the two plates, d is the distance between them, and epsilon(o) is the permittivity of free space
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electric field between two plates of a parallel plate capacitor
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E = V/d, pointing toward the negative plate
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dialectrics
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an insulator (e.g. glass, plastic, certain metal oxides) placed between two plates to lower the voltage and "make room" for more charge, effectively increasing the capacitance
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change in capacitance due to a dialectric
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C' = KC where K is the dialectric constant
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capacitors in parallel vs series
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add in parallel (each have same voltage), 1/C(s) = 1/C(1) + 1/C(2) ... and total voltage is the sum of individual voltages
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how to arrange capacitors to minimize C?
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place in series
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instantaneous current in AC
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I = I(max)*sin(2*pi*f*t) = I(max)*sin(omega*t)
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angular frequency
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omega=2*pi*f
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ordinary house current
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AC with frequency of 60 Hz
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average power
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P(rms) = I(rms)^2 *R = I(max)^2 *R*1/2
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average current of AC
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is zero, but the root mean sqare, I(rms) = I(max)/sqrt2
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potential of AC
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V(rms) = V(max)/sqrt2
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simple harmonic motion
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oscillation about an equilibrium point (where net force = zero), and subject to a linear restoring force
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linear restoring force
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always directed toward the equilibrium point, with a magnitude directly proportional to the displacement from the equilibrium (note - acceleration is therefore also proportional to displacement)
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Hooke's Law
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F = -kx where k is the spring constant (negative sign indicates that the force acts opposite to direction of displacement)
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angular frequency (of an oscillating spring)
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w = sqrt(k/m)
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acceleration (of an oscillating spring)
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a = -(w^2)x
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larger spring constant indicates..
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a stronger, stiffer spring
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for a pendulum, "k" is
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k = mg/L
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amplitude of a pendulum swing
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is its max displacement, where x = x(max) cos(wt), if x(max) occurs at t=0
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angular frequency
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w = 2*pi*f = 2*pi / T
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potential energy of a pendulum
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is gravitational potential energy = mgh
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potential energy of a spring
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U = 1/2 kx^2 (note that U=0 at equilibrium, which is where K=Kmax)
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frequency and amplitude in SHM?
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frequency and period are independt of amplitude in simple harmonic motion
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angular frequency (of a pendulum)
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w = sqrt (g/L), where L is the length of the string
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where does max acceleration occur (for SHM)?
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at maximum force, which is at maximum displacement
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constructive vs. destructive interference
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add amplitude (waves are in phase) vs. waves are 180* out of phase
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speed of a wave
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v = f*lambda = w/k = lambda/T, where k = wave number (also is the speed at which a crest or trough progagates through space)
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wave number
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k = 2*pi / lambda (note: lambda is the distance from one max to the next)
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oscillations of a wave
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y = y(max) * sin(kx - wt) where k is the wave number and y(max) is the amplitude
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longitudinal waves
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waves that have oscillations (or vibrations) that are parallel to their direction of travel; examples include sound waves and pressure waves
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transverse waves
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a moving wave that has oscillations occuring perpendicular to the direction of energy transfer; examples include an oscillating string and electromagnetic waves
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standing waves
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waves that stay in one position; this can be due either to the medium moving in the opposite direction to that of wave propagation, or of two waves moving in opposite directions leading to interference (if the latter and the amplitudes are equal, then there is on average no net propagation of energy)
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nodes
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points in a standing wave that remain at rest, i.e. have minimal amplitude (y=0)
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antinodes
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points in a standing wave that fluctuate with maximum amplitude. Occurs at points midway between nodes.
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forced oscillation
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a frequency is produced equal to the frequency of force, which is not a normal mode of vibration. The amplitude of motion will be small unless the frequency of F(applied) is close the natural frequency of the system
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resonance
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occurs when the frequency of the F(applied) is equal to a natural frequency of the system, producing a maximum amplitude of oscillation.
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resonance f of a pendulum
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f(res) = sqrt(g/L) / 2*pi = w / (2*pi)
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resonance f of a spring
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f(res) = sqrt(k/m) / 2*pi = w / (2*pi)
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sound
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a longitudinal wave produced by a mechanical disturbance propagated through a deformable medium (i.e, cannot be transmitted through a vacuum).
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speed of sound, differences in medium
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faster in solid > liquid > gas
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frequency of audible waves for humans
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f = 20 - 20,000 Hz
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infrasonic vs. ultrasonic waves
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are <20 Hz vs. > 20,000 Hz
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speed of sound in air, 0*C
|
331 m/s
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intensity of sound
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I = average rate per unit area at which energy is transported across a perpendicular surface by the wave = power/area; in units of Watts/m^2
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power of sound, carried across a surface area (e.g., an eardrum)
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P = IA, where I is (uniformly distributed) intensity and A is the surface area
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sound level
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beta = 10 log [I/I(o)], where I(o) is a reference intensity of 10^-12 W/m^2; beta is measured in decibels
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faintest sound a human can hear
|
I(o) = 10^-12 W/m^2
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pitch
|
the sensation of sound that enables one to classify the frequency of a note. It is a subjective quantity and can't be measured with instruments.
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beats
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a periodic variation in loudness created by two waves of nearly equal frequency adding together; beat frequency = |f(1) - f(2)|
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instruments and wave length
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wavelength is fixed since the standing wave corresponds to a particular note and the length of the instrument does not change; f = v/lambda
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wave velocity and temperature
|
wave velocity is proportional to the sqrt of absolute temperature... so as T decreases, velocity decreases, and the frequency (or pitch) of the sound also decreases
|
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Doppler effect
|
perceived and emitted frequencies of sound differ; if the source and detector are moving toward eachother, then the observed frequency > actual f. The opposite occurs if they are moving away from eachother.
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observed frequency in relation to actual
|
f(observed) = f *[(v + v(d)) / (v - v(s))], where v is the speed of sound in the medium, v(d) is speed of detector relative to the medium, and v(s) is the speed of source relative to the medium. If the sources are moving away from each other, you must flip the signs in the equation.
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source and detector move at same velocity - is there a Doppler effect?
|
no
|
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possible frequencies of a string attached at both ends
|
f = (nv) / (2L), derived from the fact that at length L, a string can support standing waves of lambda = 2L/n
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fundamental frequency
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or first harmonic; the lowest possible frequency of a string, f = v / 2L
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first overtone
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or second harmonic, the frequency at n=2, so f = v / L
|
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harmonic series
|
all possible frequencies that a string can support
|
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higher harmonics
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have a lower wavelength, but higher frequency... all have the same wave speed
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nodes and wavelengths in a string
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for the harmonic n, there are n half wavelengths that fit exactly along the length of the string; and there are n+1 nodes
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antinodes and pipes
|
antinodes occur at the open ends
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for a closed pipe, allowed frequencies are?
|
f = nv / 4L where n is odd integers only; L = n*lambda / 4
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how much has intensity increased if the sound is increased 20 dB?
|
a factor of 100
|
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radio wavelength
|
10^9 m - 1m
|
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microwave wavelength
|
1 m - 1 mm
|
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infrared wavelength
|
1 mm - 700 nm
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visible light wavelength
|
700 - 400 nm
|
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ultraviolet wavelength
|
400 - 50 nm
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x-ray wavelength
|
50 - 10^-2 nm
|
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gamma ray wavelength
|
<10^-2 nm
|
|
electromagnetic spectrum by decreasing wavelength
|
radio > microwave > infrared > visible light > ultraviolet > xray > gamma rays
|
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violet vs. red wavelengths
|
400 vs. 700 nm
|
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the color white
|
is light that contains all colors in equal intensity
|
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speed of light
|
the velocity of all electromagnetic waves in a vacuum (and to a first approximation in air), c = 3.00 E8 m/s
|
|
rectilinear propagation
|
light travels in a straight line through a single homogenous medium
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|
reflection
|
rebounding of incident light waves at the boundary of a medium (even if medium is transparent); the angle of rebound is equal to the angle of incident relative to the normal line
|
|
plane mirrors
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produce virtual images; parallel incident rays remain parallel after refelction from a plane mirror. The light appears to be coming from the position fo the image but does not converge there.
|
|
spherical mirrors
|
can be concave (converging, positive f) or convex (diverging, negative f). They have a center of curvature, C and a radius of curvature.
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|
focal length
|
f = the distance between the focal point and the mirror. For all spherical mirrors, f = r/2
|
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radius of curvature
|
r = distance between the center of curvature and the mirror = 2f
|
|
equation for mirrors
|
1/o + 1/i = 1/f = 2/r, where o is the distance between object and mirror, and i is the distance of the image from the mirror
|
|
real vs. virtual image
|
i is positive (image is in front of the mirro) vs. i is negative (and image is behind the mirror)
|
|
equation for plane mirrors
|
r = f = infinity, so 1/o + 1/i = zero... or i = -o, which means that the image is virtual
|
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magnification
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m = the ratio of image to object height = -i / o; a negative m signifies an inverted image, while positive is upright; |m| < 1 is a reduced image
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a ray that strikes a converging mirror parrallel to the horizontal...
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is reflected through the focal point
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a ray that passes through the focal point before reaching a convergin mirror...
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is reflectred parallel to the horizontal
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a ray that strikes where the normal passes through a converging mirror...
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is reflected at same angle to the normal
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one diverging mirror results in...
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one virtual, erect image
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one converging mirror results in...
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real, inverted image (o > f); or no image (o = f = light rays are reflected parallel to eachother and never converge); or a virtual, erect image (o < f)
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concave vs. convex (in terms of r and f)
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positive r and f, vs. negative r and f
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Snell's Law
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for refracted rays of light: n1*sin(theta1) = n2*sin(theta2), where n is the index of refraction of a medium, and theta is the angle of incident light with respect to the normal line crossing the barrier between the two mediums
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index of refraction
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n = c / v, where c is the speed of light in a vacuum and v is the speed of light in the medium (n is close to 1 for air)
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if n2 > n1
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light bends toward the normal, i.e. theta2 < theta1
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total internal reflection
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a condition where all the light incident on a boundary is reflected back into the original material, a result of any angle of incidence > the critical angle
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critical angle
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sin(theta(c)) = n2/n1; theta(c) occurs where theta1 results in theta2 = 90*... can only occur if light is passing from a higher to lower index of refraction, n1 > n2
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thin spherical lenses
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lenses have two focal point and two focal lengths; a thin lens is one whose thickness can be neglected, so F1 = F2
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converging vs. diverging lens thickness
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always thicker at the center vs. thinner at center
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converging lens and parallel rays
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converging lens causes parallel rays to converge at the focal point, and rays from the focal point to emerge parallel
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thick spherical lens
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if thickness cannot be neglected, focal length is related to curvature of the lens surface and refractive index by Lensmaker's equation
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Lensmaker's equation
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1/f = (n-1) (1/r1 - 1/r2)
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power of a lens
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P = 1/f; measured in units of dipoters when f is in meters; positive for converging, and negative for diverging lens
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lenses in contact
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a series of lenses with negligible distances between them (e.g., the eye); they behave as a single lens with equivalent focal length: 1/f = 1/f1 + 1/f2 + 1/f3... and P = P1 + P2 + P3...
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lenses not in contact
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the image of one lens is used to make the object of the next; e.g., microscopes, telescopes; magnification, m = m1 * m2 * m3...
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dispersion
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occurs when the speed of the wave varies with wavelength, for example, the splitting of white light through a prism. It occurs b/c one color of light experiences a greater refractive index than another, so it is bent differently
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diffraction
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the spreading out of light as it passes through a narrow opening (where narrow is on the order of wavelengths). It is the interference of an infinite number of waves, where each point along the slit acts as a wave source.
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zeroth fringe
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the largest bright fringe, in the center of a line of diffracted light
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location of dark fringes
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sin(theta) = n*lambda, where n is a positive integer and theta is the angle between the line drawn from center of lens to a dark fringe and the line perpendicular to the screen
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monochromatic light
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light of just one wavelength
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coherent light
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light waves whose phase difference does not change with time
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light intensity on a screen due to single-slit diffraction
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are due to constructive interference betweeen two light waves
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maxima vs. minima on a screen
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maxima: d*sin(theta) = m*lambda; minima: d*sin(theta) = (m+1/2)*lambda, where m is an integer indication the order, d is the distance between slits
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for small angles, sin(theta) equals?
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sin(theta) = tan(theta
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plane polarized light
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light in which the electric fields of all the waves are oriented in the same direction. Magnetic fields are also parallel, but convention dictates that the plane of the electric field identifies the plane of polarization
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unpolarized light
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light with randomly oriented electric fields (e.g., sunlight)
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polarizers
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only allow light whose electric field is pointed in a particular direction to pass
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blackbody
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an ideal radiator (which is also an ideal absorber, thus appearing totally black if at a lower temperature than its surroundings); can be approximated by radiation produced in a cavity with a hot object (= cavity radiation)
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Planck's constant
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h = 6.63 E-34 J*s = 4.14 E-15 eV*s
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Wien's displacement law
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lambda(peak)*T = constant = 2.90 E-3 m*K, where lambda(peak) is the wavelength at which maximum energy is emitted
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Stefan-Boltzmann Law
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total energy being emitted per unit area per second is proportional to the 4th power of the absolute temperature: E = alpha*T^4, where alpha is the S-B constant = 5.67 E-8 J/s*m^2*K^4
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photoelectric effect
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light of a sufficiently high frequency (e.g., blue or UV) is incident on a metal ion in a vacuum, causing the metal to emit an electron. The threshold frequency is dependent on the type of metal.
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energy of a photon
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E = hf, where h is Planck's constant and f is the frequency of the light... note that energy is proportional to frequency, and inversely proportional to wavelength
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if the frequency of incident light is much greater than threshold frequency of the metal...
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the excess energy is converted to kinetic energy in the electron
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max kinetic energy of an emitted electron
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KEmax = hf - W, where W is the work function of the metal = minimum energy needed to eject an e-
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minimum energy needed to eject an electron
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W = h*threshold frequency
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current of electrons produced by f > f(threshold)
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is directly proportional to the intensity of the light beam
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ionization
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the electron reaches an energy of at least 0 eV and is unbound (free from the electrostatic/Coulombic pull of the nucleus)
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fluorescence
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process in which certain substances emit visible light when excited by other radiation (usually UV). By returning to ground in two+ states, each step down emits a photon of lower frequency whose wavelength may fall in the visible portion of the spectrum
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binding energy
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amount of energy required to break up a given nucleus into its constituent protons and neutrons
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energy and mass
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E = m*c^2; the constituent parts of a nucleus have greater mass apart than they do together because of the interconvertibility of mass and energy
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mass defect
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the difference in mass between a nucleus and the sum of its constituent parts; a result of matter being converted to energy
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nucleus vs. atom radius
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radius of a nucleus is about 100,000 times smaller
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radionuclide
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a radioactive isotope
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deuteron
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H (A = 2), of deuterium
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triton
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H (A = 3), of tritium
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greatest binding energy per nucleon
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peaks at iron - implies that iron is the most stable atom. In general, intermediate-sized nuclei are the most stable
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fusion
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combine small nuclei to large (e.g., in the sun, 4H yield 1He
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fission
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split by large into small nuclei. Can be induced in some isotopes by absorption of a low energy neutron; if neutrons are released, these may cause further fission (a chain reaction).
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radioactive decay
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a naturally occurring spontaneous decay of certain nuclei accompanied by the emission of specific particles
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alpha decay
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emits an alpha particle (He-4); b/c it is doubly charged and very massive, it interacts with matter well and does not penetrate shielding very far.
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beta decay
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emission of a beta particle - an electron or positron - from a neutron or proton decaying in the nucleus.
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emission of an electron
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result of a neutron decaying into a proton and a beta-particle (or antineutrino); mass number stays the same, but atomic number increases by 1.
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emission of a positron
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result of a proton decaying into a neutron and a positron; mass number stays the same, but atomic number decreases by 1.
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antineutrino
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or beta-particle, electron
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gamma decay
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emits a gamma particle, which are high energy photons; they carry no charge, but decrease the energy of the emitting nucleus
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electron capture
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some unstable radionuclides can capture inner (K or L shell) electrons to combine with a proton and form a neutron; mass number remains the same, but atomic number decreases by 1.
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amount of sample left of radioactive sample
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(1/2)^n where n is the number of half lives
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exponential decay
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rate of decay depends on the sample size = - lambda*n, where lambda is the decay constant, and n is the sample size
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amount of sample left due to exponential decay
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n = n(o)*e^(-lambda*t), where lambda = (ln2) / half-life = 0.693 / t(1/2)
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