# Homework Help: Top speed and displacement

1. Sep 28, 2007

### aligass2004

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

Sam, whose mass is 80 kg, takes off across level snow in his jet powered skis. The skis have a thrust of 189N and a coefficient of kinetic friction on snow of 0.1. Unfortunately, the skis run out of fuel after only 12s. a.) What is Sam's top speed? b.) How far has Sam traveled when he finally coasts to a stop?

2. Relevant equations

Fk = uk(n)
F=ma

3. The attempt at a solution
I solved part A by using F-uk(n) = m(Ax). I solved for Ax, and got the answer to be 1.3815. I then used acceleration = velocity/time to find the velocity. I got the velocity to be 16.578, which is right. For part B I tried using Vxf^2 = Vxi^2 + 2(Ax)(delta x) to find the change in displacement. I got 198.936m, which was wrong.

2. Sep 28, 2007

### Mentz114

For the second part use the fact that
Frictional_force x distance = work_done_to_stop_skier = kinetic_energy_of_skier.