Physics problem on evaluating the work done by external force on a skier.

A water-skier is being pulled by a tow rope attached to a boat. As the driver pushes the throttle forward, the skier accelerates. A 67.1-kg water-skier has an initial speed of 7.4 m/s. Later, the speed increases to 10.7 m/s. Determine the work done by the net external force acting on the skier.

W =

Mass of the skier    (m)   = 67.1 kg

Initial velocity of the skier   (v) =    7.4 m/s

Final velocity of the skier (V)  = 10.7 m/s

Change in the kinetic energy of the skier 

                                                                   

                                                                    

The skier has only kinetic energy. So change in kinetic energy is equal to the work done

by the net external force working on the skier

                                      

  Answer is W= 4007.88 J

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