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Question Number 31111 by Tinkutara last updated on 02/Mar/18 | ||
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Commented by Tinkutara last updated on 02/Mar/18 | ||
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Answered by rahul@ last updated on 02/Mar/18 | ||
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Commented by Tinkutara last updated on 02/Mar/18 | ||
but why cases first and second aren't identical? | ||
Commented by momo last updated on 02/Mar/18 | ||
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$${why}\:{identical}??? \\ $$ | ||
Commented by mrW2 last updated on 03/Mar/18 | ||
Why the both cases are not identical: To keep a still object in its position you only need to fight against the gravity (static force). To stop the same object at the same position but in motion (i.e. with a speed) you must not only fight against the same gravity, you also need to rapidly reduce its speed, i.e. to give it a big negative acceleration, and acceleration means addtional force (dynamic or impact force). Therefore to stop a moving object, you need to apply a much bigger force than just to keep it in still position. Since a=v/t, we can say, the shorter the time in which you stop the moving object, the bigger the force you need to apply. | ||
Commented by mrW2 last updated on 03/Mar/18 | ||
So it is relatively easy to prevent a car to move on a slope. But it is very hard to hold it back if it is already in motion. | ||
Commented by Tinkutara last updated on 03/Mar/18 | ||
Thanks mrW2 and rahul@ Sir. | ||