Starting from rest, a skier slides 100m down a 28 D slope.....?

Question

How much longer does the run take if the coefficient of kinetic friction is 0.17 instead of 0?

I found the time for 0, but don't know how to change the formula for kinetic friction.

Answer 1

use F=m*a

for no friction
m*g*sin(28)=m*a
so
d(t)=.5*g*sin(28)*t^2
set d=100 and solve for t

for friction
m*g*sin(28)-m*g*cos(28)*0.17=m*a
now d(t)=
.5*g*(sin(28)-cos(28)*0.17)*t^2
set d=100 and solve for t

no friction
t= 6.6

friction
t= 8.0


j