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Friction and speed help

  1. Apr 29, 2008 #1
    Susan's 13.0 kg baby brother Paul sits on a mat. Susan pulls the mat across the floor using a rope that is angled 30 degrees above the floor. The tension is a constant 30.0 N and the coefficient of friction is 0.180.

    Use work and energy to find Paul's speed after being pulled 2.60 m

    So far I found the forces acting on the system to be:

    127.5N down due to gravity
    15N up due to tension
    112.5N normal force
    25.98 due to tension
    -20.25 due to friction

    So I get a net force of 5.73N which I thought if I divided by the mass of 13kg it would give me that speed, but that is wrong. I am stuck here guys.

    Thanks in advance for the help
  2. jcsd
  3. Apr 30, 2008 #2
    Force divided by mass is acceleration.

    The instructions say to use work and energy. Now that you have the net force, use that to calculate the work. And then use the change in kinetic energy to calculate the speed.
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