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Homework Help: Impulse problem: how can these two angles be different?

  1. Jul 6, 2015 #1
    1. The problem statement, all variables and given/known data

    A baseball weighing 140g is traveling to the right at 35 m/s, makes contact with a baseball bat, and then leaves the bat at 55 m/s to the left at an angle 25 degrees from the horizontal.

    I got the right answer, I how how the solution works mathematically.

    The answer is that the bat gave the ball an impulse of 12 kg m s-1 to the left at an angle of 15 degrees above the horizontal...

    This seems sooo counter-intuitive to me. How can the impulse be at a different angle from the final velocity vector that the ball got from interacting with the bat? Shouldn't they be the same angle?

    Again, I know how it works mathematically, trigonometrically...I just don't get what is happening here in a physical sense.
  2. jcsd
  3. Jul 6, 2015 #2


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    What is the relationship between impulse and momentum ?
  4. Jul 6, 2015 #3
    It's the change in momentum...I'm thinking now that the ball should leave at the same angle only if the ball were stationary. Given that the ball already had some horizontal momentum, the new "triangle of forces" created by the impact has a shorter horizontal component relative to it's vertical component if we were comparing it to the stationary ball case...so...the baseball bat is absorbing some of the horizontal momentum of the ball, giving some of it back, but not all of it, and also giving it some vertical momentum, and because the bat isn't returning all of the balls horizontal momentum, it can leave at a different angle to the impulse given.
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