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36 Cards in this Set
- Front
- Back
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simple machines |
devices that can be used to multiply or augment a force that we apply - often at the expense of a distance through which we have to apply the force |
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What is mechanical advantage? |
The ratio of output to input forces for any simple machine: MA = Fout/Fin = Iin/Iout = d1/d2 |
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What are a few examples of simple machines? |
lever, nail puller, wheelbarrrow, and crank |
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What part does statics play in? |
understanding strains in our muscles and bones |
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Why do many lever systems have a mechanical advantage of less than 1? |
many muscles are attached to joints |
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How is angular momentum defined as? |
L = I • ω |
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What are the units for angular momentum? |
kg•m^2/s |
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What is the relationship between torque and angular momentum? |
net τ = ΔL/Δt |
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When is angular momentum conserved? |
net external torque is zero |
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What is torque perpendicular to? |
the plane formed by r and f |
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Why is a gyroscope precessing around a vertical axis? |
torque is always horizontal and perpendicular to L |
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What is statics? |
study of forces in equilibrium |
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What is the equilibrium in statics? |
motion without linear or rotational acceleration |
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What is the first condition to reach equilibrium? |
net external force must be zero: net F = 0 |
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If net F is 0, then what is the net external force in each direction? |
zero; net Fx = 0; net Fy = 0 |
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What is the second condition for equilibrium? |
net external torque is zero; net τ=0 |
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What is torque? |
the rotational equivalent of a force; τ=rFsinθ |
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What is the perpendicular lever arm? |
r? = rsinθ |
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What does the perpendicular leverl arm r? represent? |
the shortest distance fr the pivot point to the line along which F acts |
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What is the SI unit for torque? |
newton-meter (N•m) |
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When is a system is equilibrium? |
net force or torque is opposite of displacement |
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When is a system in unequal equilibrium? |
net force or torque is se direction as displacement |
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When is a system in a neutral equilibrium? |
equilibriumnis independent of displacements |
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What is circular motion? |
motion with a constant angular velocity; ω=Δθ/Δt |
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What happens in non-uniform circular motion? |
velocity changes with time and rate of change of angular velocity; α=Δω/Δt |
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What does linear acceleration refer to? |
change in magnitude of velocity; at = Δv/Δt |
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What is the equation for circular motion? |
v=rω; so that at=Δ(rω)/Δt |
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What is kinematics? |
description of motion |
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What does the kinematics of rotational motion describe? |
relationships among rotation angle, angular velocity, angular acceleration, and time |
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What are the equations for average angular velocity and average velocity? |
ω- = (ω0 + ω)/2 and v- = (v0 + v)/2 |
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How proportional is angular acceleration compared to mass? |
the farther the force, the greater the acceleration |
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What is the equation for angular force? |
F=mrα |
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What is the equation of inertia? |
I = Σmr^2 |
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What is the relationship among torque, inertia, and angular acceleration? |
τ=Ια or α=net τ/Ι |
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What is the equation for rotational kinetic energy? |
KErot=(1/2)Iω^2 |
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What is the equation for work-energy theorum for rotational motion? |
netW=(1/2)Iω^2 - (1/2)Ιω0^2 |
