A 51.2-kg skateboarder starts out with a speed of 2.41 m/s. He does 104 J of wor

Question

A 51.2-kg skateboarder starts out with a speed of 2.41 m/s. He does 104 J of work on himself by pushing with his feet against the ground. In addition, friction does -226 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 7.52 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.

Explanation / Answer

a)Initial P.E. + Initial K.E. = Final P.E. + Final K.E. + 104 - 226 =>Final P.E. - Initial P.E. = (0.5*51.2*((7.52^2)-(2.41^2)))+226-104 = 1421.00288J b)mg*Change in height = 1421.00288 =>Change in height = 2.829m

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