| A | B |
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| work | the action that results when a force causes an object to move in the direction of the force ; W=F * D |
| joule | the unit used to express work and energy; equivalent ot the newton-meter |
| power | the rate at which work is done; P=W/T |
| watt | the unit used to express power; equivalent to joules per secong (J/S) |
| machine | a device that hleps make work easier by changing the size or direction of a force |
| work input | the work done on a machine; th product of the input force and the distance through which it is exerted |
| work output | the work done by a machine; the product of the output force and the distance through which it is exerted |
| mechanical advantage | a number that tells how may times a machine multiplies force; can be calculated by dividing the output force by the input force |
| mechanical efficiency | a comparison expressed as a percentage of a machines's work output with the work input; can be calbulated by dividing work output by work input and then multiplying by 100 |
| lever | a simple machine consisting of a bar that pivots at a fixed point, called a fulcrum; there are three classes of levers, based on where the input force, output force, and fulcrum and placed in relation to the load; first class levers, second class levers, and third class levers |
| inclined plane | a simple machine that is a straight, slanted surface, a ramp |
| wedge | a simple machine that is adoulble inclined plane that moves; a wedge is ofter used for cutting |
| screw | a simple machine that is an inclined plane wrapped ina sprial |
| wheel and axle | a simple machine consisting of two circular objects of different sizes; the wheel is the larger of the two circular objects |
| pulley | a simple machine consisting of a grooved wheel that holds a rope or a cable; there are two kinds of pulleys-fixed and moveable |
| compound machine | machine tha tis made of two or more simple machines |
