An astronaut throws a stone with a horizontal velocity near to the Moon’s surface. Which row describes the horizontal and vertical forces acting on the stone after release?

Question 6

An astronaut throws a stone with a horizontal velocity near to the Moon’s surface.

Which row describes the horizontal and vertical forces acting on the stone after release?

horizontal force           vertical force

A          constant                      constant

B          constant                      decreasing

C         zero                             constant

D         zero                             decreasing

Reference: Past Exam Paper – June 2015 Paper 12 Q12

Solution:

Answer: C. 

The stone is thrown near to the Moon’s surface, that is, in space.

In space, there is no air resistance. Thus, the horizontal velocity is not affected. The horizontal force is zero.

The Moon has its own gravity. The stone would fall under the effect of this force of gravity. Again, since there is no air resistance, the vertical force acting on the stone is constant.