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Energy conversion of a falling bob

  1. Jan 3, 2007 #1
    1. The problem statement, all variables and given/known data

    A bob is hung by a light string and and is pushed sideways. A peg of wood is placed vertically below the point of suspension of the string to hinder the motion of string as shown in the figure below: (please refer to the attachment)

    The bob is released. Which of the following statements is/are correct?
    (1) The bob has the largest speed when it is vertically below the peg.
    (2) The bob cannot reach the original level when it is at the right side of the peg.
    (3) The bob possesses same amount of mechanical energy at all time.

    A (1) only
    B (2) only
    C (1) and (3) only
    D (2) and (3) only

    2. Relevant equations

    3. The attempt at a solution

    I attempted option B, but the answer is C.
    For statement (1),
    I thought when it is vertically below the peg, it loses some energy to the wood, so the speed is lowered.

    Attached Files:

  2. jcsd
  3. Jan 3, 2007 #2


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    Staff Emeritus
    Science Advisor
    Gold Member

    Your attachment will take a while to be approved by the mentors, but I will try to answer your question without.

    Can I begin by asking you why you believe that the bob would lose some energy to the peg?
    Last edited: Jan 3, 2007
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