phy 121
Your 'cq_1_21.2' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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A typical automobile coasts up a typically paved incline, stops, and coasts back down to the same position.
When it reaches this position, is it moving faster, slower or at the same speed as when it began? Explain
answer/question/discussion:
Once again I believe it will be going at the same speed as when it began. I guess I am assuming that air resistance and friction are constant. Both are going to work against the direction of motion, but I am assuming that the force of air resistance and friction will be the same either going up or coming down. If they are constant, and the distance is constant then the velocity will decelerate and accelerate at the same rate because the only other force is gravity which I know remains constant.
For a real-world automobile friction would oppose motion at every position except the extreme position (where it stops for an instant), doing negative work on the automobile and causing a decrease in its KE. It would therefore end up moving more slowly than at the beginning.
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5 mins
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Again good thinking, but energy is dissipated by friction and the vehicle ends up moving more slowly than at the beginnign. See my note.
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