A rock is thrown vertically into the air. At the top of its path the net force on it is
A)less than mg.
B)mg.
C)more than mg.

Question

Quizplus · Accepted Answer

At the top of its path, the rock is momentarily at rest. Therefore, its acceleration due to gravity is 0. According to Newton's second law of motion, the net force acting on the rock is equal to its mass multiplied by its acceleration. As the acceleration is 0, the net force on the rock is also 0. Therefore, the net force is equal to the weight of the rock, which is mg (where m is the mass of the rock and g is the acceleration due to gravity). So, the correct choice is B)mg.

A Rock Is Thrown Vertically into the Air