Final Exam Chapter 14: Work, Power, and Simple Machines
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30 terms
Terms | Definitions |
|---|---|
 work | the product of force and distance is done when a force acts on an object in the direction the object moves |
| joule | SI unit for work when a force of 1 newton moves an object 1 meter in the direction of the force, 1 _____ of work is done |
| power | the rate of doing work SI unit is watt or horsepower |
| machine | a device that changes a force make work easier to do |
| What machines change | change the size of force needed, the direction of a force, or the distance over which a force acts |
| input force | force you exert on a machine |
| output force | force that is exerted by a machine |
| input distance | the distance the input force acts through |
| output distance | the distance the output force is exerted through |
| input work | the work done by the input force acting through the input distance |
| output work | the output force multiplied by the output distance |
| mechanical advantage | the number of times that a machine increases an input force |
| actual mechanical advantage | the ratio of the output force to the input force =output force/input force |
| ideal mechanical advantage | the mechanical advantage in absence of friction the ratio of the input distance to the output distance |
| efficiency | the percentage of the work input that becomes work output always less than 100% |
| simple machines | lever, wheel and axle, inclined plane, wedge, screw, and pulley |
| lever | a rigid bar that is free to move around a fixed point |
| 1st class lever | fulcrum is between input force an output force mechanical advantage: 1, >1, and <1 exs. seesaw, bottle opener, crow bar, balance |
| 2nd class lever | fulcrum, then output force, then input force mechanical advantage: always less than 1 exs. wheelbarrow, nutcracker |
| 3rd class lever | fulcrum, then input force, then output force mechanical advantage: always greater than 1 exs. baseball bat, golf club, sword |
| fulcrum | the fixed point the bar rotates around on a lever |
| wheel and axle | simple machine that consists of 2 disks or cylinders. IMA: divide radius where the input force is exerted by the radius where the output force is exerted |
| pulley | simple machine that consists of a rope that fits into a groove in a wheel IMA: equal to the number of rope sections supporting the load being lifted |
| fixed pulley | a pulley with a wheel attached in a fixed location. the direction of the exerted force is changed but the size of force stays the same IMA: always 1 |
| moveable pulley | pulley attached to the object being moved rather than to a fixed location |
| pulley system | combining fixed and moveable pulleys to achieve a larger mechanical advantage |
| inclined plane | slanted surface along which a force moves an object to a different elevation IMA: equals the distance along the inclined plane divided by its change in height |
| wedge | v-shaped object whose sides are two inclined planes sloped toward each other IMA: a thin wedge of a given length has a greater IMA than a thick wedge of the same length |
| screw | is an inclined plane wrapped around a cylinder IMA: greater IMA are screws with threads that are closer together |
| compound machine | a combination of two or more simple machines that operate together exs. car, washing machine, clock |
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