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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.

  • Physics -

    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.

  • Physics -

    Thank you! That's exactly what I did wrong. :)

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