Question

A rock is thrown straight up. What is the net external force acting on the rock when it is at the top of its trajectory (ignoring ar resistance)? a)There is none b)Gravity c)A normal force d)Thrust

Answer 1

Answer:

b) Gravity

Explanation:

Gravity acts all of the time, when you apply force to a projectile it has to be more than the forces of the gravity and air resistance together so the projectile can move,  when the rock is at the top of its trajectory the force that you applied at the beginning is getting lost, so the other forces (air resistance and gravity) make the rock fall to the floor.