Question

The skateboard on which you are standing moves as one of your feet pushes on the ground because the force you apply on the skateboard:

a. equals the force applied to you by the skateboard.
b. is larger than the force applied to you by the skateboard.
c. equals the force applied by the ground on the skateboard.
d. is larger than the force applied by the ground on the skateboard.

Answer 1

The force applied on the skateboard when pushing off with your foot equals the force the ground applies on the skateboard due to Newton's third law.

Step-by-step explanation:

The skateboard on which you are standing moves when one of your feet pushes on the ground because of Newton's third law, which states that for every action there is an equal and opposite reaction. When you push on the ground with your foot, the ground pushes back with an equal force (action-reaction pair). Thus, the correct answer to the student's question is that the force you apply on the skateboard equals the force applied by the ground on the skateboard (option c). This is also consistent with the examples of mutual forces acting and resulting in changes in momentum, such as the force of gravity between Earth and a falling object.