He must have been heading downhill !
change in kinetic energy = (1/2)(60.8)(8.12^2 - 1.84^2 ) = 1902 Joules
energy in = -278 + 90.8 = -187.2
h = 0 initially
m g h = - 1902 + 187 = - 1715 Joules
h = -1715/(60.8*9.81)
= - 2.88 meters so 2.88 is absolute value
A 60.8-kg skateboarder starts out with a speed of 1.84 m/s. He does 90.8 J of work on himself by pushing with his feet against the ground. In addition, friction does -278 J of work on him. In both cases, the forces doing the work are non-conservative. The final speed of the skateboarder is 8.12 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.
2 answers
sorry, had to drop further to make up for friction
m g h = -1902 -187 = -2089 Joules
and h = 2089/(60.8*9.81)
m g h = -1902 -187 = -2089 Joules
and h = 2089/(60.8*9.81)