- #1

uchicago2012

- 75

- 0

## Homework Statement

Accident Reconstruction.

A car, with a mass of 1600 kg, is involved in a collision. By using techniques from later chapters, we conclude it was moving 4 m/s at impact. There are skid marks leading into the collision, 18 meters long from two of the tires; no marks from the other two. If the coefficient of friction from the pavement is .92, how fast was the car going before skidding?

## Homework Equations

W

_{non}= Change in KE + Change in PE

## The Attempt at a Solution

I found the work done by the force of friction so I can use this equation:

W

_{non}= KE

_{2}- KE

_{1}+ PE

_{2}- PE

_{1}

where W

_{non}= work done by friction

but I was wondering if there were any other nonconservative forces I had to worry about. In these types of problems do you only account for things like air resistance if it specifically tells you to or should I just assume air resistance is part of the W

_{non}?

Also, since the car is on a flat surface and stays on a flat surface, Change in PE = 0, correct?

I guess I just expected this problem to be more difficult and I'm nervous I've missed something.