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Homework Help: Velocity problem

  1. Oct 6, 2009 #1
    1. The problem statement, all variables and given/known data

    A bullet with a mass of 1.5g is fired from a gun with an initial force of 500 N over 20m
    Find the initial velocity of the bullet as it leaves the muzzle.

    2. Relevant equations

    m=1.5g, F=500N, d=20m

    3. The attempt at a solution

    i cant seem to find the equation that would fit this problem any help or advice would be greatly appreciated
  2. jcsd
  3. Oct 6, 2009 #2


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    Homework Helper

    Given the force, you can find the acceleration easily.
    Have you got an accelerated motion formula with no t in it?
    There is one with just velocity, acceleration and distance that just kills this kind of question.

    If you don't have it, I suggest you find the time it takes to travel the 20 m long gun barrel (wow, long one!). Then you can use the usual accelerated motion formulas to get the speed at that time.
  4. Oct 6, 2009 #3
    i need to find the initial velocity, there is no acceleration involved i just cant find any equation that would work

    the best one ive found is v^2= (kx^2)/m but i cant find k from the info i have so im stuck. if i had k then i could solve this problem.
  5. Oct 6, 2009 #4


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    The question is poorly worded - it wants the velocity when the bullet leaves the gun and that would better be called the final velocity.
    It most certainly will accelerate with 500 N applied to .0015 kg.

    v^2= (kx^2)/m looks like a spring formula. You don't have a spring here.
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