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Phy 121
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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: ->->->->->->->->->->->-> :
I would say faster. When it began coasting uphill, it would have been much slower than when it finally stopped and started going back dowhill again. The incline would allow for a pick up in speed making it go faster when it reached the original position than when it first began.
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5 minutes
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As with the preceding, this would violate the conservation of energy.
The car starts out with a certain kinetic energy.
The gravitational force is the same going up as coming down, so the positive work it does on the car as it comes down the incline is equal and opposite to the negative work it does going up the incline. So the gravitational force makes neither a positive or a negative contribution to the net work done on the car.
Air resistance acts in the direction opposite motion, both going up and coming down.
Think through what this implies for the change in KE, then check out the discussion below for more detail.
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Then please compare your old and new solutions with the expanded discussion at the link
Solution
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