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A weight lifter picks up a barbell and ../medialib/ - lifts it chest high
- holds it for 5 minutes
- puts it down.
Rank the amounts of work W the weight lifter performs during this three operations. Label the quantities as W1, W2, and W3. Justify you ranking order.
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 Estimate the amount of work the engine performed on a 1200 kg car as it accelerated at 1.2 m/s2 over a 150 meter distance.
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A real world roller-coaster released at point A and coasting without external power would traverse a track somewhat like the figure above. Friction is not negligible in the real world. If we call the potential energy at point A relative to the ground Uo what can you say about the potential and kinetic energies UB, UB at point B and the potential and kinetic energies UC, UC at point C.
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5.  A gallon of gasoline contains about 1.3 x 108 joules of energy. A 2000 kg car traveling at 20 m/s skids to a stop. Estimate how much gasoline it will take to bring the car back to the original speed? To complicate matters further, consider the fact that only about 15% of the energy extracted from gasoline actually propels the car. The rest gets exhausted as heat and unburnt fuel.
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