Three hockey pucks collide on the ice. Hockey puck A hits hockey puck B with a force of 9N to the right. Hockey puck B hits hockey puck C at the same moment and in the same direction with a force of 4 N, not including the force from puck A. What is the resulting force on hockey puck A?

Question

Quizplus · Accepted Answer

In this problem, it is crucial to remember Newton's Third Law which is: The mutual forces of action and reaction between two bodies are equal, opposite and collinear.
Puck A collides with puck B with a force of 9N to the right. Because of Newton's Third Law, we know that puck A experiences a force that is equal and opposite, so the resultant force on A in 9 N to the left.

Three Hockey Pucks Collide on the Ice