posted by Gabby on .
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 63.6-kg water-skier has an initial speed of 5.3 m/s. Later, the speed increases to 10.8 m/s. Determine the work done by the net external force acting on the skier.
I got +5630 J, and it was wrong. I'm not sure why, or how to do it correctly.
The NET external force is the tow line force minus friction.
The net force increases the kinetic energy, by an amount
(63.6/2)(10.8^2 - 5.3^2) = 2816 J
That is the work done by net force.
It looks like you used MV^2 for the kinetic energy instead of the correct (1/2)M*V^2.
Thank you! That's exactly what I did wrong. :)