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Homework Help: Calculate the total momentum after the collision

  1. Oct 2, 2005 #1
    Hey guys, i'm stuck on this momentum question, i think I have an idea but have no way in proving it.


    (here is part c to the question)
    Calculate the total momentum after the collision. Compare this value to the total momentum before the collision. If these values differ, some likely causes of error were?

    Mass(1)= 0.55kg, Mass(2)=0.55Kg, V1 =(0.79m/s East), V2= (0m/s)
    V1 prime = (0.366m/s, 51 degrees N of E), and V2 Prime = (0.61m/s, 21 degrees S of E)

    the prime means the change in velocity after a "collision" i first thought of using (m1v1 + m2v2) =(m1v1(prime) + m2v2(prime)) but the degrees and direction are confusing me, Unless i should use vector addition to add the angles.

    Any ideas?
     
  2. jcsd
  3. Oct 2, 2005 #2

    Pyrrhus

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    Momentum is a vector quantity, so yes, Vector addition.
     
  4. Oct 2, 2005 #3
    thought so, but how would I start it off? would i find the momentums of the primes then draw it? finding the x and y componets?
     
  5. Oct 2, 2005 #4

    Pyrrhus

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    Yes.

    [tex] Info [/tex]
    [tex] |\vec{v}_{1}|= 0.366 m/s [/tex]
    [tex] |\vec{v}_{2}|= 0.61 m/s [/tex]
    [tex] \theta_{1} = 51^{o} [/tex]
    [tex] \theta_{2} = 21^{o} [/tex]

    [tex] \vec{v}_{1} = |\vec{v}_{1}| \cos \theta_{1} \vec{i} + |\vec{v}_{1}| \sin \theta_{1} \vec{j} [/tex]

    [tex] \vec{v}_{2} = |\vec{v}_{2}| \cos \theta_{2} \vec{i} - |\vec{v}_{2}| \sin \theta_{2} \vec{j} [/tex]

    [tex] \vec{v}_{R} = \vec{v}_{1} + \vec{v}_{2} [/tex]

    [tex] \vec{p}_{total} = m \vec{v}_{R} [/tex]
     
    Last edited: Oct 2, 2005
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