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Kinetic Energy vs. Momentum in Projectile collisions

  1. Feb 18, 2010 #1
    I'm trying to figure out the role that kinetic energy and momentum play in projectile collisions. there are two cases: 1.) when the projectile becomes completely embedded in the target and 2.)When the projectile completely passes through the target and flys out the other end.
    If the collision is completely inelastic in situation 1, then wouldn't the impact force just be impulse? given by the equation: Force*delta(t)=change in momentum. If this is true, then isn't the destructive force a projectile related solely to it's momentum and not it's kinetic energy? The only situation i see where having a high kinetic and low mometum is better than having really high momentum and low energy, is situation 2.

    I shoot bow and arrow, and my bow shoots a 25.7gram arrow 46.4m/sec, giving it a momentum of 1.19 kg*m/s. The energy is only 27.66J. Now compare this with a .22lr: 2.6 grams moving @ 330m/sec., which gives it only 0.858kg*m/s. But it has an energy of 141.5J.
    Although my intuition tells me the bullet will do more damage, i don't understand why.
  2. jcsd
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