friction problem?

Question

Sam, whose mass is 75 kg, takes off across level snow on his jet-powered skis. The skis have a thrust of 200 N and a coefficient of kinetic friction on snow of .1. Unfortunately, the skis run out of fuel after only 10s.
What is Sam's top speed?
How far has Sam traveled when he finally coasts to a stop?

Answer 1

Sorry I'm not up on my metric units but here's how you solve the problem.

F = ma

m = mass (75 kg)

F = net force = Thrust - friction

Thrust = 200 N

friction = Cof of Friction x weight = 0.1 (g) (mass)
= 0.1 x (9.8 M/s^2)(75 kg) that might be a N but you better check me on that part

Now you can solve the first equation for a = acceleration

Speed = Velocity = a x t t = 10 sec's

Distance under power = 1/2 a (t)^2

Coasting time will be time when Velocity = deceleration ( time)
solve for time.

deceleration = Friction force (calculated above)/ mass (given)

Coasting distance = Velocity x coasting time - 1/2 (deceleration) x (coasting time)^2

Thats all there is to it.