A 54.2-kg skateboarder starts out with a speed of 2.05 m/s. He does 96.9 J of wo
ID: 2140457 • Letter: A
Question
A 54.2-kg skateboarder starts out with a speed of 2.05 m/s. He does 96.9 J of work on himself by pushing with his feet against the ground. In addition, friction does -252 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 8.57 m/s. (a) Calculate the change (PEf - PE0) in the gravitational potential energy. (b) How much has the vertical height of the skater changed? Give the absolute value.
Chapter 06, Problem 35 A 54.2-kg skateboarder starts out with a speed of 2.05 m/s. He does 96.9 J of work on himself by pushing with his feet against the ground. In addition, friction does -252 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 8.57 m/s. (a) Calculate the change (PEf -PEo) in the gravitational potential energy, (b) How much has the vertical height of the skater changed? Give the absolute value.Explanation / Answer
a)
(PEf-PEo) = 0.5*54.2*(8.57^2-2.05^2) -( 96.9 -254 ) = -2033.6 J
b)
vertical height change = 2033.6/(54.2*9.8) = 3.83 m
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