So I figured out the first answer but I cannot figure out part b. In the sport o

Question

So I figured out the first answer but I cannot figure out part b.

In the sport of skeleton a participant jumps onto a sled (known as a skeleton) and proceeds to slide down an icy track, belly down and head first. The track has sixteen turns and drops 80 m in elevation from top to bottom. (a) In the absence of non conservative forces, such as friction and air resistance, what would be the speed of a rider at the bottom of the track? Assume that the speed at the beginning of the run is relatively small and can be ignored. (b) In reality, the best riders reach the bottom with a speed of 35.8 m/s (about 91 mi/h). How much work is done on a rider and his sled (assuming a total mass of 80.5-kg) by non conservative forces?

Explanation / Answer

a )

Potential energy = m g h

KE = 1/2 m v2

1/2 m v2 = m g h

h = 80 m

v = ( 2 g h )1/2

v = ( 2 X 9.8 X 80 )1/2

v = 39.59 m/sec

v = 39.6 m/sec ( rounded off value )

b )

intial PE = m g h

= 80.5 X 9.8 X 80

= 63112 J

final KE = 1/2 m v2

= 0.5 X 80.5 X 35.82

= 51586.01J

work done = 63112 J - 51586.01J

work done = 11525.99 J

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