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Hey all, I really need help with this homework. Any help would be appreciated

  1. Feb 1, 2012 #1
    Hey all, I really need help with this homework. Any help would be appreciated(FIXED)

    Problem: Ball of mass m hangs on a string of length L straight down from a cart of mass
    M standing on horizontal rails. The cart can move along the rails without friction.
    While the cart is at rest, the ball is given a horizontal velocity v0, v0 < sqr(2gl) directed
    along the rails.

    (a) What is velocity of the ball when it reaches
    its maximal elevation?
    (b) What is elevation h that the ball reaches
    above its original location?

    First of all hello.
    I am new to this forum and don't really know your ways yet, so please forgive me if I do something wrong. This problem has tormented me for days. I did all the other homework problems for this week and this is the last one. If anyone would help me solve the problem I would be forever grateful.

    m = mass of the ball
    M = mass of the cart
    v0 = velocity given to the ball
    V = velocity of the cart
    theta = angle between the starting position of the string and the maximal elevation of the string

    Sorry for not giving any attempts, but I really don't know where to start on this one. All i have is:
    (1/2)m(v0)^2 = (1/2)mv^2 + mgh + (1/2)MV^2
    mv0 = mvcos(theta) + MV
    I also found center of mass, in respect to the position of the ball:
    (L - mL/(M + m) = CM
    Last edited: Feb 1, 2012
  2. jcsd
  3. Feb 1, 2012 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    Hello spartanpo. Welcome to PF !

    You have some typos.

    I am unable to make sense of your question.
  4. Feb 1, 2012 #3


    User Avatar
    Gold Member

    Well, our ways are that you must show your attempts to solve the problem before we can help.
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