1. The problem statement, all variables and given/known data I've been checking out the ol' truck vs small car in a head on collision problem. The question asks which about which vehicle will experience the greatest force of impact ? The greater impulse? The greater change in momentum ? The greater deceleration. A number of aspects of it have me second guessing my understanding of what is going on....and even when I feel I may know the answer I dont actually know WHY it is the way it is 2. Relevant equations Momentum = m * v Impulse = F * t , which means a change in momentum = change in m * v Newtons 3rd law 3. The attempt at a solution So in terms of the force on impact, I believe if Newton's third law says for each action there is an equal and opposite reaction, then therefore they should impart the same amount of force on each other....although this confuses me. If F= m*a, how can they exert the same force on each other given the truck is likely to have a greater force given its mass ? The greater impulse ...I believe this would be equal. If they are exerting the same amount of force and in contact for the same amount of time then they both are creating an equal impulse. However, the change in momentum confuses me...if it = m * v, the mass of each vehicle is likely to stay the same and the velocity would stay the same. For example if the truck hits the car and pushes it east, the truck and the car will both travel east and their masses will have remained the same...therefore making the impulse equal for both ? The change in momentum...as per above wouldn't they both change by equal amounts? The greater deceleration. .for this I believe it to be the mini (or both) as A= d/t and I'm presuming the mini would end up going backwards.