# Is there a difference between contact time and impact time? (collsion)

1. Feb 13, 2013

### question dude

This is from my textbook:

I'm slightly confused about the bit underlined in red. Do you think its in reference to the sentence just before where it talks about situations of vehicles remaining tangled? (so for other cases, contact time = impact time, right?)

also, I don't really understand how to picture the scenario of the two vehicles remaining tangled together and 'how they exert forces on each other until they move at the same velocity'.

2. Feb 13, 2013

### ZapperZ

Staff Emeritus
Re: Is there a difference between contact time and impact time? (colls

You drop from 2 floors up and smash into the ground. SPLAT! Your impact time is the very short time when your velocity changes from some value v (just about to hit the ground) to zero (i.e. you are now at the same velocity as the ground). Your contact time is very long and stops until someone scrape you off the ground, i.e. the time you are in contact with the floor.

Zz.

3. Feb 13, 2013

### question dude

Re: Is there a difference between contact time and impact time? (colls

I see now. So what if you have two cars colliding head on and bouncing off each other? would contact time be the same as collision time in this situation?

4. Feb 13, 2013

### ZapperZ

Staff Emeritus
Re: Is there a difference between contact time and impact time? (colls

Correct.

Zz.

5. Feb 13, 2013

### question dude

Re: Is there a difference between contact time and impact time? (colls

many thanks!