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Work
Work and Simple Machines
Term | Definition |
---|---|
work | is done when a force exerted on an object causes that object to move some distance; equal to force times distance; measured in joules |
power | rate at which work is done; equal to the work done divided by by the time it takes to do the work; measured in watts |
input force | the force that you apply on a machine |
output force | the force that the machine applies |
mechanical advantage | how much larger the output force is compared to the input force; equals the ratio of the output force to the input force |
efficiency | the ratio of the output work to the input work; reducing the amount of friction in a machine will increase efficiency |
simple machine | a machine that does work with only one movement |
compound machine | made up of a combination of simple machines |
inclined plane | a flat, sloped surface; as inclined plane becomes longer, the force needed to move the object becomes smaller |
wedge | an inclined plane that moves; can have one or two sloping sides |
screw | an inclined plane wrapped around a cylinder or post; the more tightly wrapped the threads are, the easier it is to turn the screw |
lever | any rigid rod or plank that pivots, or rotates, around a point |
wheel and axle | consists of two circular objects of different sizes that are attached in such a way that they rotate together |
pulley | made of a grooved wheel with a rope or cable wrapped over it |
machine | makes work easier by changing the amount or force you need to exert, the distance over which the force is exerted, or the direction in which you exert your force |
joule | the unit of measurement of work |
friction | the force that acts to oppose sliding between two surfaces that are touching |
watt | the unit of measurement of power |
ideal machine | machine with 100% efficiency |
fulcrum | the point about which a lever pivots |