posted by Anonymous .
A 57.5-kg skateboarder starts out with a speed of 1.80 m/s. He does +80.0 J of work on himself by pushing with his feet against the ground. In addition, friction does -265 J of work on him. In both cases, the forces doing the work are nonconservative. The final speed of the skateboarder is 6.20 m/s.
(a) Calculate the change (ÄPE = PEf - PE0) in the gravitational potential energy.
(b) How much has the vertical height of the skater changed?