- #1

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[edit]

Does it have something to do with the direction of the conservative force field that the object is in?

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- Thread starter Hertz
- Start date

- #1

- 180

- 8

[edit]

Does it have something to do with the direction of the conservative force field that the object is in?

- #2

mfb

Mentor

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It just depends on the definition of h. If h is upwards, it is +mgh, otherwise it is -mgh.

- #3

jtbell

Mentor

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Total energy is [itex]\frac{1}{2}mv^{2}-mgh=C[/itex] for a classical non-rotating object right?

According to who? That's not what I see in the textbooks that I've used, which all have a + sign, and define h as increasing in the upwards direction.

- #4

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Total energy is [itex]\frac{1}{2}mv^{2}-mgh=C[/itex] for a classical non-rotating object right?

If you have taken the surface of the earth as the reference point for your potential energy, then the potential energy of a body of mass m at a height h (small compared to earth's radius) is mgh. It is a positive quantity with respect to the reference point. The total energy in such a case is [itex]\frac{1}{2}mv^{2}+mgh[/itex]. The Lagrangian can be [itex]\frac{1}{2}mv^{2}-mgh=L[/itex].

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