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)