A 57.5 kg skateboarder starts out with a speed of 1.75 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 6.15 m/s.
(a) Calculate the change (?PE = PEf - PE0) in the gravitational potential energy.
J
(b) How much has the vertical height of the skater changed?
m
(c) Is the skater above or below the starting point? above the starting point below the starting point