# Force of impact during collisions

1. Nov 4, 2008

### smiling_bug44

hi, i was just wondering...

if a heavy truck collides with a lighter vehicle, and both are travelling at the SAME speed, would the force of impact be:

the SAME for both vehicles,
greater on the lighter car, or
would the vehicles experience no force at all?

*edit*
hi cepheid... sorry but I'm new at the whole physics forum thing...

But i have already narrowed the answers to the question down to those three choices (though I doubt option three is the answer!)... and think that the answer could be option two... because the lighter vehicle has less mass.

Last edited: Nov 4, 2008
2. Nov 4, 2008

### cepheid

Staff Emeritus
What have you done so far? We won't do your homework for you (*because that won't help you at all*), but if you show us your work and point out where you're stuck, we can certainly point you in the right direction.

That's why it's great idea, and required (in the future) to use the template for posting homework problems. You've done part (a), which is to give a complete statement of the problem. What about part (b)? What equations or physical principles are relevant to this problem? And part (c), which is, what have you done so far?

Hint 1: what physical law applies to contact forces between bodies?
Hint 2: Even if you don't immediately know the right answer, can you at least use your knowledge of physics to *eliminate* any of the answer choices?

3. Nov 5, 2008

### smiling_bug44

> Hi, sorry about that, this is my first time using the physics forum...

Well, I know that Newton's third law would apply to this problem... which is that for every action, there is an equal reaction in the opposite direction. Now the part that I am stuck with is deciding if it's the first or second choice...

I think it COULD also be that the impact forces are the same for both vehicles, since they are traveling at the same speed... and upon collision, a force in the opposite direction of equal magnitude will act on the vehicles (the impact force). Perhaps the lighter vehicle's mass would cause it to accelerate in the opposite direction. =S

4. Nov 5, 2008

### cepheid

Staff Emeritus
A more precise statement of Newton's Third Law might be something like:

If an object A exerts a force on an object B, then B exerts a force on A that is is equal in magnitude and opposite in direction.

Does that help? Phrasing it in terms of "action" and "reaction" is imprecise and misleading, and causes a lot of conceptual/interpretation problems for people encountering this law for the first time.