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Homework Help: Got some questions

  1. Oct 17, 2006 #1
    1 Jerome pitches a baseball of mass 0.20 kg. The ball arrives at home plate with a speed of 40 m/s and is batted straight back to Jerome with a return speed of 60 m/s. What is the magnitude of change in the ball's momentum?

    A 4.0 kg-m/s
    B 8.0 kg-m/s
    C 18 kg-m/s
    D 20 kg-m/s

    2 A miniature spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 5.00 g, and the gun and puck have a combined mass of 120 g. With the system initially at rest, the radio controlled trigger releases the bullet causing the puck and empty gun to move with a speed of 0.500 m/s. What is the bullet's speed?

    A 4.80 m/s
    B 11.5 m/s
    C 48.0 m/s
    D 12.0 m/s

    3 Three satellites are launched into space connected together. Once in deep space, an explosive charge separates the three satellites and they move apart. The satellites each have different masses with m1 < m2 < m3. Which of the following statements is always true?

    A The one with mass m1 receives the greatest impulse.
    B The one with mass m3 receives the greatest impulse.
    C They all must receive equal impulses.
    D Although one or more of the above statements could be true in special cases, they are not always true.

    4 A 20-kg object sitting at rest is struck elastically in a head-on collision with a 10-kg object initially moving at +3.0 m/s. Find the final velocity of the 20-kg object after the collision.

    A -1.0 m/s
    B -2.0 m/s
    C +1.5 m/s
    D +2.0 m/s
    Last edited: Oct 17, 2006
  2. jcsd
  3. Oct 17, 2006 #2
    Seems like straightforward change in momentum/conservation of momentum problems. What are you having trouble with.
  4. Oct 18, 2006 #3
    I missed the class and don't know how to set it up so if you could show me how to set it up and the answer i'll try it and see if i get it right thanks
  5. Oct 18, 2006 #4


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    Homework Helper

    1) If you know the definition of momentum, then you'll know how to define a change in momentum, too.

    2) Use the fact that momentum is conserved.

    3) Start off with the definition of impulse.

    4) What is conserved in an ellastic collision?
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