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Homework Help: Conservation of Energy-please help me

  1. Nov 5, 2008 #1
    Conservation of Energy--please help me!!

    1. The problem statement, all variables and given/known data
    A block is pushed against the spring with spring constant 5.7 kN/m (located on the left-hand side of the track) and compresses the spring a distance 4.6 cm from its equilibrium position. The block starts at rest, is accelerated by the compressed spring, and slides across a frictionless track except for a small rough area on a horizontal section of the track. It leaves the track horizontally, flies through the air, and subsequently strikes the ground. The acceleration of gravity is 9.8 m/s^2.

    1) What is the speed v of the block when it leaves the track?

    2) What is the horizontal distance x the block travels in the air?

    3) What is the total speed of the block when it hits the ground?

    2. Relevant equations

    KE = (1/2)mv^2
    Ue = (1/2)kx^2

    3. The attempt at a solution

    To find velocity I set KE equal to Ue (def. of conservation of energy)
    (1/2)mv^2 = (1/2)kx^2
    mv^2 = kx^2

    v = sqrt [(kx^2)/m]
  2. jcsd
  3. Nov 6, 2008 #2


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    Homework Helper

    Re: Conservation of Energy--please help me!!

    That sounds right for (1). For (2) and (3) you need the height it falls, so I hope you've been given that. And I don't know what the deal with this rough area is. Have they given you any more information about that? Because if it slows the block down by friction, conservation of energy will be useless.
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