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Basic questions about momentum

  1. Mar 30, 2010 #1
    I am a little confused about how momentum works.

    If the mass were to increase, would the velocity also increase?
    If the mass were to increase, would the momentum also increase?
    If the mass was to decrease, would the velocity also decrease?
    If the velocity was to increase, would the momentum also increase?

    I was told that if mass were to decrease, then the velocity would actually increase. I'm not sure if this is true, so if someone could answer these questions, I'd appreciate it!
  2. jcsd
  3. Mar 30, 2010 #2
    Hi there

    Hope this is acurate, and might be worth double checking.

    What I know is momentum = mass x velocity
    Call momentum p

    Lets take a car with mass 500kg movin at velocity 1m/s
    p = m x v
    = 500 x 1
    = 500 kg.m/s

    Now the same mass at a slower velocity of 0.9m/s
    p = m x v
    = 500 x 0.9
    = 450 kg.m/s
    here we have a decrease in p

    Now lets look at a bullet with mass 5g moving at 400m/s
    p = m x v
    = 0.005 x 400
    = 2 kg.m/s
    So the the momentum is not great here
  4. Mar 30, 2010 #3
    If you are keeping momentum constant, then, as the equation dictates, if mass goes down, velocity must go up. if velocity goes down, then mass must go up. once again, this is only if momentum is constant.

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