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Homework Help: Find velocity with projectile and recoil accelerations

  1. Sep 10, 2015 #1
    1. The problem statement, all variables and given/known data

    A rolling projectile launcher is initially at rest. Then internal compressed air accelerates the projectile through a distance L in a pipe (see diagram). The acceleration of the projectile with respect to the pipe is ap. During the launch the launcher has a recoil acceleration ar with respect to the ground. Both accelerations are constants. Use the data given below and calculate the velocity, with respect to the ground, of the projectile as it leaves the pipe.

    Data: L = 2.00 m, theta= 53.0, ap = 36.0 m/s2. ar = 15.0 m/s2

    Projectile launcher.png

    2. Relevant equations
    Constant acceleration equations

    3. The attempt at a solution
    I have never seen anything like this before. However, I tried setting up it up like a projectile motion problem with what I knew

    Xo=0 Yo=0 because at rest then accelerations would ax= 36cos(53)-15 and ay=36sin(53)

    I just wanted to put this out there and see if I am remotely near the path of solving this problem correctly
  2. jcsd
  3. Sep 10, 2015 #2


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    Staff: Mentor

    That is a possible approach I guess. You know the vertical acceleration, and you can calculate the height difference the projectile covers in the barrel. That should help to find more parameters.
  4. Sep 10, 2015 #3
    Are you saying vertical acceleration as the acceleration due to gravity?
  5. Sep 10, 2015 #4
    Any body have any more guidance or hints?
  6. Sep 11, 2015 #5


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    Staff: Mentor

    Ignore gravity. The origin of the acceleration is not relevant here.

    How much is the top of the barrel above the bottom?
    You accelerate an object vertically with acceleration ay. How long does it take to reach this height?
    I didn't forget the thread, but if you don't get answers between 1 AM and 2 AM (central European time) it is not hard to guess why. No reason to add such a post.
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