Gpe (1 Viewer)

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hi i dont under this GPE thing

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the formula is = -G r

but when u lift an object up into the air.. doesn;t its GPE increase

according to this it would decrease.

so as im CLOSER to the surface of the Earth is my GPE larger or smaller.

im also confused since this thing is negative

so does larger mean close to zero.. or is it larger magnitude?

help plz thanx

 

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If you lift the object into the air, "r" increases, meaning that the absolute value of the GPE decreases. However, since GPE is negative, this "decrease" turns into an increase (i.e. the GPE goes from a big negative to a smaller negative, which means it's getting bigger).

The GPE is negative because the "zero point" for the measure of GPE is taken as a point very, very far away from the body generating the gravitational field. If GPE is 0 at this very far distance, as you get closer to the centre of the field the GPE gets smaller because it is defined as the energy required to move an object from the infinte point to a certain spot in a gravitational field (not by how 'high' it is). Basically, as you get closer, the gravitational attraction increases and moves the object closer (that's my understanding), so the GPE is a negative value (since the field is providing the energy to pull in the object, a negative work is being done by the object). To escape the gravitational field, this energy must be supplied to the object (and hence to move against the gravitational field you need to supply energy, not the other way round). I'm a little hazy on this concept myself so if anyone else knows better feel free to correct me.


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