...Potential Energy

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1.

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, KB at point B and the potential and kinetic energies UC, KC at point C.



2.

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.



3.

A 10 kg sled slides down a 30 degree slope. Because of friction it maintains a constant speed. For every meter of travel, the energy lost to friction (in joules) is

98

98 x sin30

98 x cos30

none of above





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