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33 Cards in this Set
- Front
- Back
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force
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a push or a pull. it can be observed on object if the object moves
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work
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work= force x distance; a force being applied over a distance
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power
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power = work/time; how much work is done in a certain amount of time
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joule
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the unit we use to measure work
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watt
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the unit we use to measure power
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mechanical efficiency
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work output/work input x 100%; how efficient a machine is
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mechanical advantage
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force output/ force input; how much a machine multiplies your input force
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input work
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what you physically do to a machine
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output work
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what the machine does to an object
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machine
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anything that we use to make work easier
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friction
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what opposes motion; this is why machines are not 100% efficient
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incline plane
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a ramp; it makes work easier by increasing the distance which the object must travel
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wheel and axle
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an axle surrounded by a larger wheel; makes work easier
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lever
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a straight bar that makes work easier by pivoting around a point
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fulcrum
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a fixed point that a lever pivots around
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pulley
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a grooved wheel with a rope or chain running through it to make work easier
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screw
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a cylinder wrapped with an inclined plane
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wedge
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two inclined planes back to back usually used to cut things
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complex machine
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a combination of 2 or more simple machines
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describe a real life situation where force and motion are occurring but no work is being done.
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carrying a backpack home ( no work because force and motion are not in the same direction )
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describe a real life situation where work is being done.
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picking a backpack off the floor ( force and motion are in the same direction )
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state and be able to to use the formula used to calculate work.
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work = force x distance ( distance must be in meters )
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state and be able to use the formula for power.
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power = work/ time ( time must be in seconds )
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how can power be increased/
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1. do more work in the same amount of time
2. do the same work in less time |
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can a machine be 100% efficient ? why or why not?
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no, all machines have moving parts that generate friction. some work input must be used to overcome friction
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state an example and the advantage of the following machines: fixed pulley
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fixed pulley: ex. flagpole or blinds, this machine makes work easier by changing the direction of the input force
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state an example and the advantage of the following machines: wheel and axle
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wheel and axle: ex. door knob, this machine makes work easier by allowing you to use less force over a greater distance
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state an example and the advantage of the following machines: inclined plane
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inclined plane: ex. ramp or slide, this machine makes work easier by allowing you to use less input force over a greater distance
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state an example and the advantage of the following machines: wedge
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wedge: ex. knife, this machine makes work easier by allowing you to use less input force over a greater distance
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state an example and the advantage of the following machines: screw
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screw: ex. jar lid, this machine makes work easier by allowing you to use less input force over a greater distance
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draw a real life example of a 1st 2nd and 3rd class lever. then label the effort force, fulcrum and load or resistance force for each lever
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1st class lever: the fulcrum is between the effort (input force) and the load (resistance force) This make the work easier by changing the direction of the input force. Ex. see-saw
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draw a real life example of a 1st 2nd and 3rd class lever. then label the effort force, fulcrum and load or resistance force for each lever
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2nd class lever: the load (resistance) is between the fulcrum and the effort (input) force. This makes work easier by allowing you to use less input force force over a greater distance. ex: wheelbarrow
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draw a real life example of a 1st 2nd and 3rd class lever. then label the effort force, fulcrum and load or resistance force for each lever
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3rd class lever: the effort is between the load (resistance) and the fulcrum. This machine makes work easier by, multiplying your input distance (meaning input force is greater). ex: baseball bat, hockey stick
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