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BB Gun Muzzle Velocity

  1. Jun 15, 2009 #1
    1. The problem statement, all variables and given/known data

    A student decides to measure the muzzle velocity of a pellet shot from his gun. He points the gun horizontally. He places a target on a vertical wall a distance x away from the gun. The pellet hits the target a vertical distance y below the gun.
    (a) Show that the position of the pellet when traveling through the air is given by y = Ax^2, where A is a constant.
    (b) Express the constant A in terms of the initial velocity v and the free-fall acceleration g.
    (c) If x = 3 m and y = 0.21 m, what is the initial speed of the pellet?


    2. Relevant equations



    3. The attempt at a solution
    Can I assume vi is constant? For (a) I got y=x^2[g/(2vi^2)]. Is vi a constant? If so then I know to do it. If not can you help? Thanks.
     
    Last edited: Jun 15, 2009
  2. jcsd
  3. Jun 15, 2009 #2

    PhanthomJay

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    The initial velocity is of a given magnitude and direction. While instantaneous velocity might change, the initial velocity is just a constant. Your equation, however, is almost correct, but not quite.
     
  4. Jun 15, 2009 #3
    Hmm I tried it over and I still get the same answer. What did I do wrong?
     
  5. Jun 15, 2009 #4

    PhanthomJay

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    O,so sorry, you are correct, I was reading your equation incorrectly.
     
  6. Jun 15, 2009 #5
    Ok thanks for your help.
     
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