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58 Cards in this Set
- Front
- Back
What is the difference between vectors and scales? |
Scales only have magnitude and vectors have a magnitude and direction |
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What is a lever used for? |
To change the direction of movement and to trade the magnitude of the effect for the distance over which the effect is applied |
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Name 3 uses of moments |
Brake levers Hammers Wheelbarrows |
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If an object is in equilibrium what can we conclude? |
There is no net force acting in any direction There is no net turning effect about any point |
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What's the equation for shear stress? |
Force/area parallel to the force |
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What are the three kinds of forces? |
Tensile Compressive Shear |
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What's an axial load? |
A load directed across the axis of the member |
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What is a tension force? |
A force which stretches a material |
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What is a tensile force? |
A force which produces tension which increases the length of the material which it's acting on |
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What's compression? |
A force that squeezes or crushes a material |
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What's a shear force and what can it cause a material to do? |
It's a force which slides one face of a material over an adjacent face that stretches the material. It can cause a material to bend, slide or twist |
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What is stress |
The ratio of the applied force to the cross sectional area of the material |
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What is strain? |
The ratio of the change of length to the original length |
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What does hooke's law state? |
The extension is proportional to the load applied |
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On a stress/strain graph, up to which point does a material obey hooke's law? |
The limit of proportionality |
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What's the young's modulus? |
The ratio of stress to strain |
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What are elastic materials? |
Materials which go back to their original shape once a load is removed |
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What is the elastic limit equal or close To? |
The limit of proportionality |
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When does plastic deformation happen? |
When a material is stretched beyond its elastic limit |
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What's ductility? |
The ability of a material to undergo plastic deformation without fracturing |
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What's is brittlenes and what do they have? |
It's the lack of ductility and they have hardly any plastic stage which means that the elastic stage is followed by immediate fracture |
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What's malleability? |
The ability of a material to be shaped while cold by hammering or rolling |
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What's the factor of safety? |
The ratio of the ultimate stress to the working stress |
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What's newton's first law? |
A body acted on by no net force moves with constant velocity and zero acceleration |
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What's Newton's second law? |
If a net force acts on a body, the body accelerates and the direction of acceleration is the same as the direction of the net force |
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What's Newton's third law? |
Each force produces an equal and opposite reaction force |
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What's inertia? |
It's the resistance to a change in motion |
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What is Mass? |
The amount of matter in a body |
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What does mass measure? |
How much gravity the mass exerts on other bodies and how much the body itself will resist acceleration |
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What are the assumptions that we make for freely falling bodies? |
They be treated as particles Only motion will be in a straight line No turning or spinning Constant acceleration |
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What's momentum? |
The product of a bodies mass and velocity |
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What are impulsive forces? |
Forces which act for a very short period of time |
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What's the equation for an impulse? |
Impulse=applied force*time=change in momentum |
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What's one radian? |
The angle subtended at the centre of a circle by an arc with a length equal to the radius of a circle |
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What is work? |
It's when someone or something applies a force to an object which makes it move |
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What is power? |
The rate at which work is done |
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What's the equation for power? |
Work done/time |
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What's energy? |
A measure of the ability to do work |
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What's kinetic energy? |
Energy stored in an object because of its motion |
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What's potential energy? |
The energy stored in an object due to its position in a gravitational field |
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What's efficiency? |
The ratio of output to input |
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What's the difference between liquids and gases? |
Liquids have a fixed volume and gases expand to full their container Liquids are difficult to compress and gases are highly compressible |
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What's density? |
The mass per unit of volume |
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What can density be measured by? |
A density flask |
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What's density? |
It's the ratio of a substances density to some standard density (usually water) |
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What's viscosity? |
A measure of the resistance to shape deformation |
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What are hydrostatic systems? |
Systems where the fluid in them is at rest or the movement of the fluid is relatively small |
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What are examples of hydrostatic systems? |
Piezometers Monometers Barometers Hydraulic jacks Presses Brakes |
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What is pressure and what is it measured in? |
Pressure is the force per unit area acting on a surface and is measured in Pascals |
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What are the four factors governing pressure? |
The pressure at a given depth is equal in all directions. The pressure at a given depth in a fluid is independent of the shape of the container. She a pressure is applied to a fluid it's transmitted equally in all directions. Pressure acts perpendicular to the surface containing the fluid |
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What does the pressure depend on? |
The density of the fluid The acceleration due to gravity The height of fluid vertically above the point |
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What does pressure equal |
Density*acceleration due to gravity*height |
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What's atmospheric pressure? |
The pressure that the air exerts on all points of the earths surface |
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What's absolute pressure? |
Pressure above that of an absolute vacuum |
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What's guage pressure? |
The pressure above that normally present due to the atmosphere |
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What's the equation for absolute pressure? |
Gauge pressure+Atmospheric pressure |
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What pressure will you most likely be given? |
Gauge pressure unless told otherwise |
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What's 1 bar equal to |
100 000Pa |