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Homework Help: Conservation of Energy pinball problem

  1. Nov 7, 2006 #1
    The ball launcher in a pinball machine has a spring with a force constant of 1.10 N/cm (Fig. P5.71). The surface on which the ball moves is inclined 10.0° with respect to the horizontal. If the spring is initially compressed 5.00 cm, find the launching speed of a 0.100 kg ball when the plunger is released. Friction and the mass of the plunger are negligible.


    so here's what i did

    Ei = Ef, so

    1/2kx^2 = mgsin@x + 1/2 mv^2

    I got .377 m/s for the answer, but the real answer is 1.61 m/s

    Plz tell me what i did wrong.

    Thank You
  2. jcsd
  3. Nov 7, 2006 #2


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    Science Advisor

    Apparently you did the arithmetic wrong. I used your formula and got 1.61 m/s (actually, I got 161 but then realized I was still in cm/s !)
  4. Nov 7, 2006 #3
    ohhh, i made the same mistake too, except convert on of them to m but not all. Thank You
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