Question

An Olympic luge (sled) track has a vertical drop of 160 m and a length of 1600 m. A typical slider and her sled have a combined mass of 100 kg. Assume that she starts effectively from rest at the top of the track and reaches a final speed of 40 m/s (90 mph) at the bottom. 1. Find values for both the work done on her by gravity and the work done by non-conservative forces. 2. Assuming the only non-conservative force that does work is sliding friction, find an average value for Hk(Note that drag from the air is important at these speeds; but we are simply ignoring that).

Answer 1

Here,

1.

for the work done by gravitational force

work done by gravitational force = m * g* h

work done by gravitational force = 100 * 9.8 * 160

work done by gravitational force = 156800 J

work done by non-conservative forces = work done by gravity - final kinetic energyt

work done by non-conservative forces = - 156800 + 0.50 * 100 * 40^2

work done by non-conservative forces = - 76800 J

2. let the average value of uk

angle of sled = asin(160/1600) = 5.74 degree

work done = uk * Normal force * L

- 76800 = - uk * 100 * 9.8 * sin(5.74 degree) * 1600

uk = 0.49

the coefficient of friction acting is 0.49