# Homework Help: Calculating force of collison

1. Sep 13, 2012

### h9376w

This isnt officially a homework question, just a problem/discussion that has arisen at work.....

so, basically we are looking to find out which would have a greater impact:-

a 1500kg vehicle travelling at a constant speed of 50mph

or

a 2000kg vehicle travelling at a constant speed of 30mph

we are basing this on impact with a stationary object with no movement, eg a solid wall.

Now i know that F = MA, but with the speed being constant then surely there would be no acceleration?

is there anyway we can calculate this with just the information provided? or does stopping time/distance have to get involved (as this is just a theoretical question, we havent actually got any of these factors)

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 13, 2012

### CAF123

Well, you could calculate the impulse (or change in momentum) of the cars assuming when they hit the wall, they stop. If you define positive x right, then the impulse will be in the negative x direction, same direction as the force exerted by the wall. To find the magnitude of the force exerted on the cars by the wall requires their time of contact.

3. Sep 13, 2012

### h9376w

ok, so that would probably work.......

can you explain how i would go about working that out?

:)

4. Sep 13, 2012

### CAF123

Have you come across the concept of impulse and momentum?
Use the relation, $$Ft = m(v-u).$$ This is essentially F = ma but inputting a kinematic relation which describes constant acceleration. As I said before, with the given data you can only compute the quantity Ft, known as impulse.
See here : http://en.wikipedia.org/wiki/Impulse_(physics [Broken])

Last edited by a moderator: May 6, 2017