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Old Aug 4th 2008, 07:21 PM   #1
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Force

Why force must exist in opposite direction than increasing gravitational potential energy??
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Old Aug 5th 2008, 07:11 AM   #2
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Originally Posted by werehk View Post
Why force must exist in opposite direction than increasing gravitational potential energy??
Sure it can. So I can only assume that you mean a specific force, but I can't think of what would prompt this question. So what force are you talking about?

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Old Aug 5th 2008, 08:46 PM   #3
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For example, we are always pulled by gravity
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Old Aug 7th 2008, 03:56 PM   #4
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Originally Posted by werehk View Post
For example, we are always pulled by gravity
Barring any other forces in the problem and any internal changes in energy we have
$\displaystyle \vec{w} \cdot \vec{s} = mg (- \Delta h) \equiv - \Delta PE$

The basic idea is that when we increase the height we are "winding up" the potential energy because when released the object has more energy to give.

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