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Work? maybe just kinematic (please help! I don't even know what it is!)

  1. Oct 16, 2006 #1
    Work?....maybe just kinematic...(please help! I don't even know what it is!)

    The spring shown in the figure is compressed 50 cm and used to launch a 100 kg physics student. The track is frictionless until it starts up the incline. The student's coefficient of kinetic friction on the 30 degree incline is 0.15.


    What is the student's speed just after losing contact with the spring?

    How far up the incline does the student go?

    The v_initial is incredibly easy to find, 14.1, but I can't seem to find how far he travels up the incline.
    I've set it up a few different ways, and each time I get the wrong answer.

    if Fx = -F_f - F_w*sinθ = ma
    Fy = n - F_w*cosθ = 0 -> n = m*g*cosθ

    then shouldn't -umgcosθ - mgsinθ = ma
    giving you a = -g(ucosθ + sinθ) ?

    and then the distance could be solved using the v_initial and a using kinematics?
    But it is wrong? Could someone please explain?
  2. jcsd
  3. Oct 16, 2006 #2
    never mind found it
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