1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    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


    User Avatar

    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 :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook