Define gravitational field strength.
The mass of a spherical comet of radius 
is approximately 
. Assuming that the comet has constant density, calculate the gravitational field strength
on the surface of the comet.
A second comet has a length of approximately 
and a width of approximately 
. Its outline is illustrated in the figure below.
Suggest one similarity and one difference between the gravitational fields at the surface of this comet and at the surface of the comet in (b).
.
