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Homework Help: Newbie needs muchos help (thanks)

  1. Oct 22, 2009 #1
    newbie needs muchos help!!!(thanks)

    right so i am new to the forums and am really glad i found them.any way just doing some revision and have come across this and i am stumped.

    Q:In a particular type of hardness test a steel hammer is allowed to fall on a material being tested.If the hammer bounces to a height of 400mm determine:

    a) The initial velocity immediately after bouncing on the specimen, and

    b) The times when the hammer is at a height of 300mm.

    take g= 9.8m/s/s

    now i am stumped to find the initial velocity as in my mind i dont have enough information to fill an equation.

    please help this is killing me!!

    (this is probably really easy but i am a newbie and need the help)

    thanks in advance
  2. jcsd
  3. Oct 22, 2009 #2
    Re: newbie needs muchos help!!!(thanks)

    The initial velocity of the hammer will be the same as the final velocity of the hammer right before it hits. (unless you are accounting for lost energy when it hits)
  4. Oct 22, 2009 #3


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    Staff: Mentor

    Re: newbie needs muchos help!!!(thanks)

    Welcome to the PF. I'm not sure about the before-bounce part (unless they are assuming a perfectly elastic collision with no energy lost in the bounce), but after the bounce is easy. Just use the standard kinematic equations for distance and velocity with gravity being the acceleration factor.

    Can you list the equations for us, and start to try to use them to solve the post-bounce part?
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