Show that the acceleration
of a particle moving in a straight
line can be written, in terms of its velocity v and its displacement x
from a point of the line, in the form
.
At a distance x km from the centre of the Earth the gravitational
acceleration in km s-2 is given by the formula c/x2 where
c=4 ×105. If a space craft 104 km from the centre of the
Earth is moving directly away from it at a speed of 10 km s-1
at what distance will it be moving with half that speed?