work done and P.E


by BillyCheung
Tags: work
BillyCheung
BillyCheung is offline
#1
Dec8-03, 12:14 AM
P: 10
Dear all

I know that E(grav) = -GmM / r, Can I use Work done = F x s to calculate the P.E between two mass of the space? Thank a lot.Good Bye

Billy
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KLscilevothma
KLscilevothma is offline
#2
Dec8-03, 03:26 AM
P: 321
Originally posted by BillyCheung
Dear all

I know that E(grav) = -GmM / r, Can I use Work done = F x s to calculate the P.E between two mass of the space? Thank a lot.Good Bye

Billy
No, I don't think so because F isn't a constant in a G-field, but we can use integration to derive the formula, E(grav) = -GmM / r.

dw = - F dx

[tex]\int ^{w'}_{0} dw = - \int ^{\infty}_{r} \frac{GMm}{x^2} dx[/tex]

[tex]w' = -\frac{GMm}{r} [/tex]

Where w' is the work required to take an object from infinity to a particular point in a G-field, with distant r away from the other object.


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