Talk:Work (physics)/Archives/2012/October

K11-K12 version

I am not sure what Lookang meant by K11-K12 version, but I believe the edit was to be something like what follows:

The gravitational potential Φ(r) at a point in gravitational field around mass M, such as a planet, is defined as the work done in bringing a mass from infinity to that point. The force of gravity on a mass m is directed along the line connecting the two bodies, M and m,

$F=-{\frac {GMm}{r^{2}}},$

where G is the gravitational constant and r is the distance between the two bodies.

The work of this force on the particle m from infinity to the distance r is given by

$\Phi (r)=-\int _{\infty }^{r}{\frac {GMm}{r^{2}}}dr={\frac {GMm}{r}}{\bigg |}_{\infty }^{r}={\frac {GMm}{r}},$

because dividing by infinity yields zero. Prof McCarthy (talk) 02:49, 18 October 2012 (UTC)