Posted by James on Monday, May 27, 2013 at 12:29pm.
Starting from rest, a skier slides 100 m down a 28 degree slope.How much longer does the run take if the coefficient of kinetic friction is 0.17 instead of 0?

Physics  MathMate, Monday, May 27, 2013 at 6:40pm
Case 1: zero friction
F=mg sin(28)
a=F/m=g sin(28)
S=ut+(1/2)at²
100=0+g sin(28)t²/2
t=sqrt(2*100/(g sin(28))
=6.59 s.
Case 2: μ_{k}=0.17
Frictional force
=μmg cos(28)
Net force (assuming μcos<sin)
=mg(sin(28)μcos(28)
t=sqrt(2*100/(g (sin(28)μcos(28))
=7.99 s
Take the difference.

Physics  Frank, Monday, October 10, 2016 at 1:55am
shouldn't case 1 be cos(28) lol
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