physics
posted by dave .
A 64.2kg skier coasts up a snowcovered hill that makes an angle of 23.8° with the horizontal. The initial speed of the skier is 7.18 m/s. After coasting 1.96 m up the slope, the skier has a speed of 3.13 m/s. Calculate the work done by the kinetic frictional force that acts on the skis.

when up vertically 1.96 sin 23.8
call that h = 1.96 sin 23.8
gain in potential energy = m g h
inital Ke = (1/2) m (7.18)^2 = initial total Energy
final total energy = (1/2)m(3.13)^2+m g h
loss to friction = inital total  final total
= (1/2)m(7.18^23.13^2) mgh 
842.72 J