# Inelastic Car Crash problem. HELP!

1. Apr 2, 2004

### UniGal

The problem is: The red car rear ended the blue car(who was stopped at a stop sign, with handbrake partly on) the cars ended up seperately on the other side of the intersection. We are asked to explain what happened, was the driver of the red car speeding etc. I am unsure how to start this problem. We are not given any velocities. The red car has skidmarks starting from the exactly place of collision with the blue car. What formula would u use? How would i start it? To me it seems that we don't have enought info.
Cheers
Erin

2. Apr 2, 2004

### holly

I don't think you are supposed to solve this one with numbers, but with the conservation of momentum idea. The red car was speeding, as shown by the skid marks beginning at point of impact. To make marks of any real length, you must be speeding, unless the accident occurred on some street with a high speed limit. To arrive at the other side of the intersection separately, since the blue car was stopped AND had the handbrake partially on (they drive like I do), the red car had to impart a big old impulse to the blue car. I think the skid marks are the key along with the final position of both cars. About how far is it across a typical 2-2 intersection? 30 feet or so? At 60 mph, you're going 88 feet per second. To hit something stationary and even dragging its feet and push it that far...that sounds like speeding was involved, but I don't really know. I can't puzzle it out. Can you bug your professor for clarification?

3. Apr 2, 2004

### UniGal

yeah thanks i'll give it another go.