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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Assignment 21 Seed Question 2
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
When the automobile goes up to the top of the incline, it is standing still so it isn’t moving and has no speed. When it is at the bottom, in its original position, it should be at the same speed it started with. This is because of the law of conservation of energy. The kinetic energy will be the same as it was when it started to travel up the hill, but in the opposite direction. If we look at the equation KE = ½ m v^2, we see that as KE is the same, the quantity of v^2 must be the same (although, it is very important to note that v and KE do not increase or decrease by the same amount, since the quantity of v is squared). Another way of thinking of this is to see that both sides of the equation must be equal, and since the mass stays the same, the velocity must change by the same rate.
Good.
Note that for a real-world automobile friction would oppose motion, 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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This took me about 10 minutes to do.
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&#Good responses. See my notes and let me know if you have questions. &#