56.  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. In the 2010 Winter Olympics, the track had sixteen turns and dropped 126 m in elevation from top to bottom. (a) In the absence of nonconservative 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 gold-medal winner (Canadian Jon Montgomery) reached the bottom in one heat with a speed of 40.5 m/s (about 91 mi/h). How much work was done on him and his sled (assuming a total mass of 118 kg) by nonconservative forces during this heat?

Frank Gunn/AP/Wide World Photos

Absence of non-conservative forces implies conservation of mechanical energy

 

 

Assume starting from rest and make the bottom of the track the zero of gravitational potential energy and we have

 

Solve speed at the bottom

 

 

 

Since we are now allowing non-conservative forces we must use modified work-energy

 

 

 

 

 

 

 

 

 

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This page last updated on January 11, 2020