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# Work and Machine

### KAL Work and Simple Machines

What is work? transfer of energy that occurs when a force makes an object move.
What must happen for work to be done? a force must make something move
How are work and energy related? When work is done, a transfer of energy must always occur.
What are the 2 conditions for work to be done on an object? 1)object has to move and 2)motion of the object must be in the same direction as the applied force
What is the equation for work? Work = force X distance: force in newtons and distance in meters =work in joules
What is a machine? device that makes doing work easier
What are the three ways to make work easier? 1) incresaing force-bottle opener or car jack; 2) increasing distance -ramp3) changing direction-an ax
What is mechanical advantage? number of times a machine multiplies an effort force
What are the six types of simple machines? lever, pulley, wheel and axle, inclined plane, screw, and wedge
Describe the three classes of levers? first class fulcrum in the middle (seesaw); second class resistance force in the middle wheelbarrow; third class effort force in the middle (swinging a bat)
What is mechanical advantage of a lever? length of effort arm divided by length of resistance arm
What is mechanical advantage of a pulley or pulley system number of ropes supporting the load
What is mechanical advantage of an inclined plane? effort distance (length of slope) divided by resistance distance (height of slope)
What is a compound machine? Two or more simple machines working together. example -can opener
What is a lever A bar that is free to pivot, or turn, about a fixed point (fulcrum).
What is a pulley? grooved wheel with a rope running along the groove
What is a wheel and axle? 2 wheels of different sizes that rotate together
What is an inclined plane? a sloping surface that reduces the amount of force required to do work
What is a screw? inclined plane wrapped in a spiral around a cylindrical post
What is a wedge? inclined plane with one or two sloping sides. It changes the direction of the effort force.
What is power? amount of work done over time. Work in joules divided by time in seconds gives power in watts
Efficiency work (out)/ work (in) x 100
Why can't efficiency of a machine be 100%? Work is lost in the movement of machines in the form of friction.
Created by: klaud