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Homework Help: Velocity of a projectile fired horizontally from a spring launcher ballistic pendulum

  1. Feb 29, 2012 #1
    I am trying to determine the velocity of a ball fired horizontally from ballistic pendulum. The data is as follows:
    ball mass: 62.2 g
    spring mass: 14.7 g
    rod mass: 89.3 g
    length of spring: 126.1 mm
    initial spring length: 5 cm
    compressed spring length: 1 cm
    k: 2.05 N/m calculated from previous experiment

    Using the Work-Kinetic Energy Theorem
    Kbo + Kro + Kso = Kb + Kr + Ks
    .5mv^2oball + .5mv^2orod + .5kx^2 = .5mv^2ball + .5mv^2rod - .5kx^2
    I took all the terms to 0 and got v_oball = (kx^2 /m_ball)^.5.

    this doesn't seem correct, shouldn't the mass and lengths of the spring and rod be used?

    2nd part is to determine the range it should travel from a height of 101.05 cm above ground fired horizontally.
    I used the R = v^2 /g sin2t but since angle t= 0 I am getting 0 for the range.
    Last edited: Feb 29, 2012
  2. jcsd
  3. Mar 1, 2012 #2


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    welcome to pf!

    hi lip1993! welcome to pf! :smile:

    (try using the X2 button just above the Reply box :wink:)
    i don't understand the set-up :redface:

    do you mean a ball fired horizontally at a ballistic pendulum (from a spring)? :confused:
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