Asmall rock remains at rest in outer space while an astronaut pushes horizontally on it with a force of 20 n. which of the following must be true? a. there is another horizontal force acting on the rock. b. there are vertical forces acting on the rock. c. the rock is extremely massive. d. the rock does not feel the gravitational pull of earth.

Option A

Explanation:

The rock is initially at rest; this means that there are no net forces applied to the rock, so it can be moving at a constant speed or at rest.

The astronaut is pushing with a force of 20N (horizontally), then we have that there must be another force (equal in magnitude but in opposite direction) acting on the rock, that opposes the 20N force that the astronaut is doing.

Then the correct option is A, there is another horizontal force acting on the rock