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7Sci Chapter 20
Work & Machines
| Question | Answer |
|---|---|
| What is a device that makes work easier by changing the size or direction of force? | machine |
| What is the work done by a machine on an object? | output force |
| What is the work that you do on a machine? | input force |
| What is the number of times the machine multiplies force? | mechanical advantage |
| What is a comparison of a machine's work output with the work input? | mechanical efficiency |
| What equation would you use to find mechanical advantage? | MA=output force/input force |
| What causes machines not to be 100% efficient? | friction |
| What is a example of a person doing work on an object? | a crossing guard raising a stop sign that weighs 10N |
| What simple machine was used by the Egyptians to build pyramids? | inclined planes and levers |
| If a barbell weighs 160N, what other information do you need to calculate how much work it takes to life it? | how high the barbell is being lifted |
| What machine always has a mechanical advantage of less than 1? | a poorly lubricated, movable pulley |
| What does a fixed pulley change? | the direction of a force |
| When a machine increases the size of the force exerted, what happens to the distance? | it must increase |
| What type of simple machine is a screw? | wheel and axle |
| What is it called when a force causes an object to move in the direction of the force? | work |
| What is the rate at which power is transferred? | energy |
| What do you call the number of times a machine multiplies force? | mechanical advantage |
| What is a machine that is made of two simple machines? | compound machine |
| What is machine with a grooved wheel that holds a cable? | pulley |
| A moving object has what kind of energy? | kinetic |
| How does a ramp make lifting a heavy object easier? | less force is needed to move the object over a longer distance |
| Where is the input force of a wheel and axle exerted? | a circular distance |
| What is an example of a compound machine? | block and tackle pulley |
| What two things must happen for work to be done? | the object must move in the same direction as the force |
| What is a doorknob an example of? | wheel and axle |
| What type of lever places the load between the input force and the fulcrum? | a 2nd class lever |
| What type of pulley is attached to something so it does not move? | a fixed pulley |
| What is a bar that pivots on a fulcrum called? | a lever |
| What is the SI unit equivalent to 1 Newton-meter called? | joule |
| What is a machine that has 100% mechanical efficiency? | an ideal machine |
| What is F x d used for? | to calculate work |
| What is kinetic energy? | a moving object that has this type of energy |
| What is power? | the rate at which energy is transferred |
| What is a watt? | the unit used to express power |
| What is W ÷ t used for? | to calculate power |
| What is a first class lever? | a lever where the fulcrum is between the input force and the load |
| What is a second class lever? | a lever where the load is between the input force and the fulcrum |
| What is a third class lever? | a lever where the input force is between the fulcrum and the load |
Created by:
masonteach
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