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2 questions

  1. Sep 11, 2005 #1
    Hey ,


    I need to verify my work about this problem:
    Two small objects A and B are suspended from the ends of a rope thrown over a pulley. Object A is at 1.2 m above B when the system is at rest. Object A descends with a downward acceleration of 0.3m/s2 and because of the rope, B accelerates upward at the same rate. How much time elapses before the objects bump each other?

    I found t=2seconds


    A softball picher pitches a ball at 65 mph.
    The distance from the pitcher's mound to home plate is 43ft, but the pitcher realeases the ball about 41 ft from the home plate.
    a- How long does it takes for the ball to reach home plate? (I found it t=.43s)
    b-A Good pitcher can make the ball curve left about 6 inches over the pitch distance. If this is due to a constant acceleration, what is its magnitude and which direction does it act?

    For this second question I do not know how to do it
    need some suggestions

    Thank you
  2. jcsd
  3. Sep 11, 2005 #2


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    Homework Helper

    The first two answers are correct.

    For IIb, the ball curves to the left, so the acceln must be in the same dirn, no!!

    You are given the distance moved - 6 inches - and the time taken - the time for the pitcher to reach the home plate.
    Use the standard eqns of motions now.
  4. Sep 11, 2005 #3
    question (bis)

    Sorry, but I still dont get perhaps I have difficulty to represent the scene . I do not know baseball well!!
    but I continue searching!
  5. Sep 11, 2005 #4


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    Homework Helper

    Forget the baseball.

    Consider the question as:

    A particle, starting from rest and moving under a constant acceleration, moves a distance of 6 inches in 0.43 sec. What is its acceleration ?

    When the baseball is thrown, it has an intial velocity of 65 mph, but that is in the forward direction, from mound to plate. It won't have any (initial) velocity in the sideways direction, just a small amount of acceleration.
    Last edited: Sep 11, 2005
  6. Sep 11, 2005 #5
    ok! Thanks I see what to do now!!
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