1. Not finding help here? Sign up for a free 30min 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!

Need help finding change in velocity and momentum

  1. Mar 28, 2013 #1
    An automobile of mass 1500 kg traveling at 24 m/s crashes into a similar parked automobile. The two automobiles remain joined together after the collision. Suppose that the collision last for 0.020s, and pavement with a coefficient of friction uk=0.63. What change of momentum and what change of speed does the friction force produce in the joined automobiles in the interval of 0.020 s ?

    Delta p=?
    Delta v=?

    for p I did 24m/s *1500kg=36000
    3600/12m/s=3000
    The Friction force = µ . m . g =0.63*9.81*3000=18541 N
    The change in momentum produced by this force = F . t =18541*0.02=371 kg*m/s
    delta p=36000-371=35629 kg*m/s

    to get v
    35629/3000=11.87m/s
    12m/s-11.87m/s=0.15 m/s
     
  2. jcsd
  3. Mar 28, 2013 #2
    What exactly do you need help with?
     
  4. Mar 28, 2013 #3
    the numbers that I input are apparently wrong.
     
  5. Mar 28, 2013 #4
    I am not sure what you mean by this. I have checked your computations and my results agree with yours.
     
  6. Mar 28, 2013 #5

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Does the offending vehicle have its brakes on?
     
  7. Mar 28, 2013 #6
    it does not
     
  8. Mar 28, 2013 #7

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    So... what's the error in the equation I quoted?
     
  9. Mar 29, 2013 #8
    I should have used 1500kg for mass instead.
     
  10. Mar 29, 2013 #9

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    Exactly. Does it accept your answer now?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Need help finding change in velocity and momentum
Loading...