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Net Force (calculating time?)

  1. Jun 9, 2009 #1
    Scientists are experimenting with a kind of gun that may eventually be used to fire payloads directly into orbit. In one test, this gun accelerates a 5.0 kg projectile from rest to a speed of 4.29 km s-1. The net force accelerating the projectile is 0.47 MN. How much time is required for the projectile to come up to speed? (Answer to 2 s.f.)

    I have absolutely no idea how to do this...Any help is appreciated! Thanks
  2. jcsd
  3. Jun 9, 2009 #2


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    Welcome to PF kiwisj.

    Have you learned about impulse?
    Can you give a definition or some relevant formula for it? Or describe in words what it is?
    What units does it have?
    Last edited: Jun 9, 2009
  4. Jun 9, 2009 #3
    F = ma
    F= 0.47 MN= 4.7E5 N
    m= 5 kg

    Plug it in and solve for a ...

    a=92000 m/s^2

    Δv = a * t
    Δv= 4.29km/s= 4290 m/s
    a=92000 m/s^2

    Solve for t and I got ....

    t = 0.047s
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