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Homework Help: Impulse momentum questionsplease need some help

  1. Nov 15, 2004 #1
    hi guys im a college junior...taking physics for the first time in my life...its fun...but still tuff...just can i get help with these couple questions..i mean it would be very gracious of any of u to help me out...i know im new and all, but this place...i was just browsing around and it rocked sooo....and

    wow i never new this place existed....i might come here much more often

    question 1: a 3.0 kg body is initially moving northward at 15m/s. Then a force of 15N, towards the east acts on it for 4.0 s (a) At the end of the 4.0 s, whats the body's final velocity? (b) what is the change in momentum during the 4.0 s?

    i know the answers...can you just show me how to work out part A??? i got 60 for part B, and keep getting 25 for part A, but thats not it....

    i would really appreciate this...thank you...illpost the other 3 questions as well ?
  2. jcsd
  3. Nov 15, 2004 #2
    The position of three particles written as (x,y) coordinates are, particle 1 (mass 4.0 kg) at (4.0m, 0m); particle 2 (mass 6.0kg) at (2.0m, 4.0m); particle 3 (mass 3.0 kg) at (-1.0m, -2.0) what is the location of the center of mass????

    this one too pleasE?? how do you do it...i have answers...
  4. Nov 15, 2004 #3
    A projectile of mass 2.0 Kg approaches a stationary target body at 8.0 m/s. The projectile is deflected through an angle of 90.0 degrees and its speed after the collision is 6.0 m/s. WHat is the speed of the target body after the collision is perfectly elastic????

    any help on how to do this one guyzz??
  5. Nov 15, 2004 #4

    ok i solved this one, so dont need it thanks...
  6. Nov 15, 2004 #5
    Considering this is propably one of the easiest exercise you can make of newton's second law and constant acceleration, you should really try solving it again. Keywords: Newton's second law and motion with constant acceleration ;)
  7. Nov 15, 2004 #6
    brother i am doing it,....the answer i am getting is 35...teacher says it is 25....what am i doing wrong inthe calculations????
  8. Nov 15, 2004 #7


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    Perhaps, if you showed us your solution, we could help find the error.

    Also, we have a homework help forum, just for this type of post.
  9. Nov 15, 2004 #8
    My guess is you are forgetting that the directions of the two velocities are different (first 15m/s to north and second caused by the force is to east).
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