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Homework Help: A head-on Collision (Example #7) page 205 Cutnell & Jhonson Physics 8e

  1. Aug 4, 2014 #1
    One ball has a mass of m1 = 0.250 kg and an initial velocity of 5.00 m/s. The other has a mass of m2=0.800 kg and is initially at rest. No external forces act on the balls. What are the velocities of the balls after the collision?

    Elastic Collision.
    On the book I have this formula.

    STEP 1#

    1/2 m1vf1^2 + 1/2 m2Vf2^2 = 1/2 m1V01^2 + 0

    (I am confused for the 1/2 at the beginning and why is squares?)

  2. jcsd
  3. Aug 4, 2014 #2


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    Gold Member

    That is the formula of KE and states that the sum of the energy of the balls will be equal to 1/2 0.250*5^2 = 3.125J
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