# Head-on collision with a car equal to ones own vehicle

1. Sep 28, 2011

### dfmjr49

i could use some help with a question:

if one realizes that one is about to have a head on collision with a car equal to ones own vehicle, is it better for one to speed up on the theory that the harder i hit him the less it hurts me, or is it better to slam on brakes to lessen the impact? i have always heard, the harder you hit someone else the more it hurts them than me. is this this true and why?
thank you

2. Sep 28, 2011

### daveb

It's better to slow down. Think of it this way. Would you rather hit a brick wall at 5mph or at 50mph?

3. Sep 28, 2011

### Naty1

If either party reduces speed, kinetic energy is reduced and benefits both. You can also try to imagine what would happen if you hit the other car at,say, 1,000 mph....likely your engine would end up in the back seat of your car...and maybe the other car as well...

4. Sep 28, 2011

### dfmjr49

thanks...but help me here. the brick wall isn't moving. is the same with the car? when i played football i was always told the harder i hit him the less it will hurt me. was that bs from the coach...who by the way, wasn't by any means a physics professor

5. Sep 28, 2011

### sophiecentaur

The 'Physics' answer is that you should slow down (both of you, ideally).
The football scenario is much more complicated because players are 'actively' colliding - they are probably using their muscles and senses during the collision, which could be changing the situation whilst it is happening. Also, players are not at all like 'point masses'. Their mass is distributed vertically. If you tackle (rugby tackle) hard / fast enough and low down, you may unstick his legs from being fixed to the ground and cause his body to rotate. Then there could, indeed, be less force against your shoulder because you would be transferring less momentum - whilst still bringing him down.
Then there's the psychological thing. Get him scared of you on the first impact and the next ones may be a lot easier. Definitely no Physics involved there.

6. Sep 28, 2011

### abelanger

For football, one reason it would less hurt you is because you were more ready for impact (ie muscles were ready, better body/leg/shoulder/etc position) therefore there is less chance for you to get a sprained ankle to injured shoulder. As for the car: slow down.

7. Sep 28, 2011

### mrspeedybob

You reminded me of this...

Last edited by a moderator: Sep 25, 2014
8. Sep 29, 2011

### Lsos

Remember that for every action, there is an equal and opposite reaction.

So if you hit the other car harder, it will hit you back just as hard.