ap physics
posted by clueless on .
Starting from rest, a 10.2 kg block slides 2.90 m down a frictionless ramp (inclined at 30.0° from the floor) to the bottom. The block then slides an additional 4.80 m along the floor before coming to a stop. Determine the coefficient of kinetic friction between block and floor.

ap?
the block has mgh of PE when it starts, so at the bottom all that energy is kinetic.
Now, friction absorbs this energy, so
mu*mg*distance=mgh
solve for mu
Notice the distance is independent of mass. Neat experiment to show this. 
distance down = 2.9 sin 30 = 1.45 meter
Ke at bottom = U at top = m g h = m*g*1.45 Joules
Work done by friction = that KE
mu m g * 4.8
so
m*g*1.45 = mu m g *4.8
mu = 1.45/4.8
note m g cancels 
I am the one who nocks just put that in