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Homework Help: Acceleration and Deacceleration

  1. Oct 13, 2008 #1
    A bullet leaves the barrel of a rifle at 1000 m/s. If the gun barrel is 50 cm long, what is the acceleration of the bullet?

    For this problem, I used v^2 = u^2 + 2ax, but got like 1000000 m/s^2 for my answer. Is this right? It seems like a ridiculous solution.

    A driver sees a slow moving vehicle 100 meters ahead. He de-accelerates at -4 m/s^2. He overtakes the vehicle 5 seconds later. Given that the faster vehicle is now going half its original speed, what is the speed of each vehicle as the faster vehicle passes?

    For this one, do I use the same formula or should I use another one?
  2. jcsd
  3. Oct 13, 2008 #2


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    If you assume constant acceleration then your solution is correct. 1x106 m/s2 is not unreasonable for the acceleration of a bullet.
    That formula should be fine.
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