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!

Princip. of linear impulse and momentum , diff. btw. impulsive force and non-impulsiv

  1. Jan 29, 2012 #1
    when applying the principle of linear impulse and momentum , how do I know if the force should be considered impulsive or non-impulsive , how should I know if I should consider it in the equation , I already know that an impulsive force is a force that is applied for a very short time ,but in some problems forces such as the normal force were considered impulsive ,for example , there is one containing a crate where the only forces applied are the weight ,normal force ,and friction and still momentum was not conserved , for example , the princip. of impulse and momentum is m(v1) + ∑ ∫ (F)dt =m(v2)
    when do I consider the integral to be 0 and momentum conserved
    Thank You
     
  2. jcsd
  3. Jan 29, 2012 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    hi tj00343! :smile:
    i don't understand :redface:

    friction isn't for a very-short time …

    obviously friction over a finite distance (and time) will change the momentum :confused:

    can you give a more specific example?​
     
  4. Jan 29, 2012 #3
    Re: princip. of linear impulse and momentum , diff. btw. impulsive force and non-impu

    And Momentum is conserved only when there are no external forces acting on the system.
    ∫Fdt gives the change in momentum for both impulsive and non-impulsive forces,so what is the problem?
     
  5. Jan 29, 2012 #4
    Re: princip. of linear impulse and momentum , diff. btw. impulsive force and non-impu

    I thought that momentum is conserved when there are no external forces on the system or the forces acting are non-impulsive forces ....I'm confused because in problems my professor solved , in some problems there was external forces acting on the system ,but they were not considered ,if for example 2 balls collide , their weights and normal forces are external to the system yet we apply conservation of momentum to find their velocities ........
     
  6. Jan 29, 2012 #5

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    ah, but momentum is a vector,

    so conservation of momentum is a vector equation

    (and so is Newton's second law)

    so it works in each direction separately …

    in your professor's examples, the weights and normal forces are vertical,

    so there is no horizontal external force or impulse,

    so horizontal momentum is conserved :smile:
     
  7. Jan 30, 2012 #6
    Re: princip. of linear impulse and momentum , diff. btw. impulsive force and non-impu

    ahhhhh thank youuu tiny tim................and pabloenigma
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Princip. of linear impulse and momentum , diff. btw. impulsive force and non-impulsiv
  1. Impulse and forces (Replies: 17)

  2. Momentum and Impulse (Replies: 6)

Loading...