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Homework Help: Swinging Pendulum hits Block on Table- Find Distance and Acceleration?

  1. Nov 8, 2011 #1
    1. The problem statement, all variables and given/known data
    A 1.00 kg pendulum hanging from a length 1.50 m starts horizontal to the ceiling and swings (until it's perpendicular to the ceiling) to hit a 4.00 kg block. The coefficient of friction is .30.
    a) What distance does the block travel?
    b) Assuming there is no friction, what would be the acceleration of the block?
    So given:
    m_p=1.00 kg
    l=1.50 m
    m_b=4.00 kg
    μ = .30

    2. Relevant equations
    PE = mgh
    KE = 1/2 mv^2
    v_f - v_i = 2ad

    3. The attempt at a solution

    A) So I can find the final velocity of the pendulum by setting PE=KE and solving for v, and then solving for a using the third equation listed. But first, what would I use for d in that 3rd equation, since the pendulum's path is circular?
    Next, once I have a, I was simply going to give the block that value of a to start with, and use F= ma_1 = ma_2 - f and solve for a_1 which would be the actual acceleration of the block taking into account frictoin, and then just use that to find the distance.
    Is this process correct, and how do I find the distance traveled by the pendulum?

    B) Wouldn't this just be the acceleration of the pendulum, since no friction is slowing it down?
  2. jcsd
  3. Nov 8, 2011 #2
    Wait a second, to find the change in distance, would I find the distance of the curve or just the displacement?
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