A skateboarder with his board can be modeled as a particle of mass 71.0 kg, loca
ID: 2176851 • Letter: A
Question
A skateboarder with his board can be modeled as a particle of mass 71.0 kg, located at his center of mass (which we will study in a later chapter). As shown in the figure below, the skateboarder starts from rest in a crouching position at one lip of a half-pipe (point ). The half-pipe is one half of a cylinder of radius 7.00 m with its axis horizontal. On his descent, the skateboarder moves without friction so that his center of mass moves through one quarter of a circle of radius 6.50 m. Find his speed at the bottom of the half-pipe (point ). m/s Immediately after passing point , he stands up and raises his arms, lifting his center of mass from 0.500 m to 0.900 m above the concrete (point ). Next, the skateboarder glides upward with his center of mass moving in a quarter circle of radius 6.10 m. His body is horizontal when he passes point , the far lip of the half-pipe. As he passes through point , the speed of the skateboarder is 4.85 m/s. How much chemical potential energy in the body of the skateboarder was converted to mechanical energy in the skateboarder-Earth system when he stood up at point ? Your response differs from the correct answer by more that 10%. Double check your calculations. J How high above point does he rise?Explanation / Answer
chemical energy converted=energy at C-energy at D
=m*11.32/2 +mg0.9-m*4.852/2 -mg*6.1=76.09 J
2)mgh=76.09
h=76.09/(71*9.81)=0.109m