SIMPLE MACHINES NOTE A

# SIMPLE MACHINES NOTE A - WARMUP 1 Why does it take more...

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WARM–UP: 1) Why does it take more work to move something over a rough surface than over a smooth surface? ANSWER : Some of the work applied to the object is lost in overcoming friction. Thus, you need to supply more energy than normal in order for the object to move. 2) Is E E friction static friction kinetic , , > , E E friction static friction kinetic , , < or E E friction static friction kinetic , , = ? ANSWER : Observe that F F friction N = μ which implies that E F d friction friction = Δ = E F d friction N μ Δ . In general, μ μ static kinetic > since F F static kinetic > . Thus, E E friction static friction kinetic , , > . MACHINES : tools or devices that transmit or modify energy to perform or assist in the performance of tasks. Simple machines are simple tools used to make work easier. Compound machines have two or more simple machines working together to make work easier. 1) INCLINED PLANE : The inclined plane is a plane surface set at an angle, other than a right angle, against a horizontal surface. The inclined plane permits one to overcome a large resistance by applying a relatively small force through a longer distance than the load is to be raised. Lifting a heavy box onto a loading dock is much easier if you slide the box up a ramp--a simple machine. PROBLEM : Compare the work done by moving a 10 kg mass vertically as opposed to sliding it up a ramp inclined 30° to the horizontal. (Assume no energy loss due to friction)

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