Question

A 90-kg ice hockey players collides head on with an 80-kg ice hockey player. If the first person exerts a force of 450N on the second player, how much force does the second player exert on the first?

Answer 1

Solution: The Newton’s 3^rd law states that if a body 1 exerts a force F₁₂ on body 2, then body 2 also exerts a force F₂₁on body 1 which is equal in magnitude but opposite in direction.

Thus we have

F₁₂ = F₂₁                                (equal magnitudes)

In vector notation,

F₁₂ = - F₂₁                                            (equal magnitude, opposite direction).

Thus a 90 kg hockey player exerts a force of F₁₂ = 450 N on 80 kg hockey player, then 80 kg hockey player too exerts a force of F₂₁ = 450 N (magnitude) which is opposite in direction.

Thus the answer is 450 N.