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Homework Help: Show that the initial speed is vi = sqrt 2gL(l-cosθ).

  1. Jan 11, 2009 #1
    1. The problem statement, all variables and given/known data
    An object of mass m is suspended from the top of a cart by a string of length L. The cart and object are initially moving to the right at a constant speed vi. The cart comes to rest after colliding and sticking to a bumper, and the suspended object swings through an angle θ.
    (a) Show that the initial speed is vi = sqrt 2gL(l-cosθ).
    (b) If L = 2.0 m and θ = 40.0°, find the initial speed of the cart.

    2. Relevant equations
    KE = PE
    1/2mv2 = mgh
    L1= L-(Lcosθ)

    3. The attempt at a solution
    1/2mv2 = mgh
    v2 = 2mgh/m
    v = sqrt 2gh
  2. jcsd
  3. Jan 11, 2009 #2


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    Homework Helper

    Did you draw a diagram? Look at the situation. How can you express the height the object moves through in terms of the length of the string?
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