- #1

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Kindly Clarify! Thanks a LOT!

- Thread starter ehabmozart
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- #1

- 213

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Kindly Clarify! Thanks a LOT!

- #2

Doc Al

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ΔE = ΔKE + ΔU = 0

Therefore: ΔU = - ΔKE

- #3

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I know that.. I meant about the intuition ... WHy is it U 1 - U2 and not the opposite

- #4

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Are you talking about this in the context of mechanics relating to work?

- #5

Doc Al

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I'm not sure I understand the issue. One goes up while the other goes down.I know that.. I meant about the intuition ... WHy is it U 1 - U2 and not the opposite

Just a note about what Δ means: When going from 1 to 2, ΔU = U

- #6

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I still don't get the point!

- #7

Doc Al

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How about giving a specific example that illustrates your question.I still don't get the point!

- #8

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When, let's say you throw in a rock upwards, we know conceptually that the work done is negative since the weight is directed downwards and the displacement is upwards, also, the gravitational potential energy is given by U = mgh (m = mass, g = acceleration due to gravity, h=height (relative to some reference)). The equation W=U1-U2 is consistent with this, when we throw a rock upwards, U2>U1 and hence W<0 (negative), in the other case when we drop a rock, U2<U1 and hence W>0 (positive). Thus the equation is consistent with our idea of work.

I think, this would help if you want a more intuitive approach on this.

- #9

jtbell

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This is incorrect. By definition, ΔU = UWhy is it the difference in gravitational potential energy is given by U grav 1 - U grav 2

For an object falling freely under the influence of gravity, U

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