# Homework Help: Car hits wall momentum

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1. Nov 4, 2016

### niveda

1. The problem statement, all variables and given/known data
The question is asking when a car hits a wall, will the car or the wall experience the greater force.
2. Relevant equations

3. The attempt at a solution
I believe it's the equal force because of newtons 3rd law

2. Nov 4, 2016

Correct.

3. Nov 5, 2016

### Lokendra1799

Analysing the Car, there is a large change in momentum of the car (Impulse acts on it) and if we analyse the wall, the initial velocity was zero and the final velocity is also zero..so Impulse must be zero.
Car has more impact than the wall. You are right that the Third law of Newton beholds here. I think the question might be asking about the impact?

4. Nov 5, 2016

### Staff: Mentor

When we see a question with a casual statement like "a car hits a wall", we reflexively invoke the simplifying assumption that the wall is immovable in order to concentrate on presumably more interesting aspects of the problem. Our assumption is equivalent to assigning an effectively infinite mass to the wall or at least to whatever the is holding the wall in place.

While the impulse that the wall experiences must be identical to what the car experiences thanks to Newton III, the results in terms of motion must be interpreted in light of our assumptions: We don't expect any finite force integrated over finite time to cause an infinite mass to move.