Question

Jack is trying out a new skateboard that he got for his birthday. He puts one foot on the skateboard and the other foot on the ramp. He notices that when he pushes off of the ramp with his foot, his body and the skateboard move forward up the ramp. He wants to investigate this phenomenon to answer the question: What causes this motion? He determines that he needs to figure out which force pair is involved with the motion he experiences.

Answer 1

Newton's third law of motion explains how Jack starts his skateboard moving.

This law states that every action has an equal and opposite reaction. This means that forces always act in pairs. First an action occurs—jack pushes against the ground with his foot.