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How is momentum conserved in a Gauss Gun?

  1. Apr 10, 2017 #1
    1. The problem statement, all variables and given/known data
    So for those who aren't familiar with the Gauss Gun here is a video demonstrating its function:

    As you can see in the video, a steel ball is rolled towards a sequence of magnets and other steel balls and as the incoming ball strikes the magnet, the ball on the other end ejects at a higher velocity. NOTE: in the video there is recoil but in my case there isn't recoil as the magnet is stuck in place.

    2. Relevant equations
    Momentum is calculated by mass*velocity.

    3. The attempt at a solution
    But this doesn't make sense to me as both the incoming and outgoing steel balls have the same mass but they travel at different velocities so when momentum is calculated, isn't the momentum different and means that momentum isn't conserved in this system?

    Please clarify this for me as I've been struggling with this concept for quite a while and can't get my head around it. I would also like to have an equation for showing the conservation of momentum for multiple variations of this setup.

    Thanks in advance
     
  2. jcsd
  3. Apr 10, 2017 #2

    BvU

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    Hello Adriano, :welcome:

    Did you read some of the explanations ? Anything unclear :smile: ?
     
  4. Apr 10, 2017 #3
    Hi, I've come across this website before and just gives explanations to do with Kinetic Energy and not momentum. I'm specifically asking how momentum is conserved in this system.

    Thanks!
     
  5. Apr 10, 2017 #4

    BvU

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    Momentum is not conserved: energy is drawn from the magnetic configuration and used to accelerate the balls (just before they bump into the magnet).

    Look at it this way:
    To reload, you must do mechanical work: exercise force to peel the sticking balls back from the magnets. To peel it off is more work than you get back when it ckicks onto the preceding ball again (becasue it's further from the magnet by 1 ball diameter). That's exactly what the link tells you.
     
  6. Apr 10, 2017 #5
    Oh right I see, so momentum isn't conserved in this system?

    I've looked at many other websites on this and some say momentum is conserved so I'm quite confused.
     
  7. Apr 10, 2017 #6

    CWatters

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  8. Apr 10, 2017 #7

    BvU

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    I stand corrected... (had looked at the next video where the magnets were 'fixed' in place and never gave it a second thought). o:)
     
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