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Difference between Impulse and Momentum

  1. Aug 9, 2013 #1
    What's the difference between impulse and momentum ?

    When do we use impulse or when do we say a body has impulse ?
     
  2. jcsd
  3. Aug 9, 2013 #2
    Hello.

    If a body experiences an impulse, its momentum changes. So if a force acts on an object in a short amount of time, that object will experience an impulse, and subsequently its momentum will change.
     
  4. Aug 9, 2013 #3
    momentum is a property of moving objects...mass x velocity.
    To change momentum requires a force acting for a length of time.
    The quantity Force x time is called impulse and it equals the change in momentum.
    So I would say impulse is used to link force with momentum.
     
  5. Aug 9, 2013 #4
    F = ma, where a = Δv/Δt. Therefore FΔt = mΔv.

    The left hand side is the impulse and the right hand side is the momentum. Both are vector quantities.
     
  6. Aug 9, 2013 #5
    technician and mark.watson both are on the right track, but I would say technician is assuming a constant force, while mark.watson is giving an infinitesimal form of the actual definition:

    The definition of impulse I is
    [tex]\vec{I}=\int \vec{F} \ dt [/tex] Impulse is a time integral of force.
    Momentum, on the other hand, is a property of an object. If an impulse I is imparted on an object, it will change that object's momentum by [itex]\vec{I}[/itex]. To be more explicit, if the object initially has momentum [itex]\vec{p}[/itex], and then an impulse [itex]\vec{I}[/itex] acts on that object, its final momentum will be [itex]\vec{p}+\vec{I}[/itex]. So an impulse is basically momentum transferred.
     
    Last edited: Aug 9, 2013
  7. Aug 9, 2013 #6

    jtbell

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    Staff: Mentor

    Impulse is to momentum as work is to kinetic energy.

    Work-energy theorem: ΔK = W (the change in an object's kinetic energy equals the work done on it)

    Impulse-momentum theorem: Δp = I (the change in an object's momentum equals the impulse acting on it)
     
  8. Aug 9, 2013 #7
    Well, work can go into potential energy too, e.g. stretching a spring.
     
  9. Aug 17, 2013 #8
    Thanks a lot guys :)
     
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