1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Impulse, Momentum, and Baseball

  1. Oct 23, 2006 #1
    A baseball has mass 0.145 kg.

    A. If the velocity of a pitched ball has a magnitude of 45.0 m/s and the battered ball's velocity is 55.0 m/s in the opposite direction, find the magnitude of the change in momentum of the ball.

    delta p = m*delta v = m*(v2 -v1) = .145 kg (-55.0 m/s - 45.0 m/s) = -14.5 kg*m/s

    B. Find magnitude of impulse applied to it by bat.

    J = F*delta t = delta p = -14.5 kg*m/s ?? Is it the same as the above?

    C. If the ball remains in contact with the bat for 2.00 ms, find the magnitude of the average force applied by bat.

    J = Avg. F*delta t

    delta t = 2.00 ms(1s/1000 ms) = .002 s

    Avg. F = J/delta t = (-14.5 kg*m/s)/.002 s = -7250 N ?

  2. jcsd
  3. Oct 23, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    All good. (Since they ask for magnitudes only, your answers should be positive.) And yes, since impulse equals change in momentum, the answers to A and B are the same.
  4. Dec 1, 2007 #3
    why should the answer be positive ? iam kind of confused I thought it depended on what velocity is positive and negative
  5. Dec 1, 2007 #4


    User Avatar

    It comes from the formula for magnitude - 2d = sqrt(x^2 + y^2). Even if x or y were negative, -x * -x = +x^2. There are no square roots of negative numbers (apart from complex numbers).
  6. Dec 1, 2007 #5
    The answers should be positive, since they are asking for the magnitudes. The negative sign gives you the direction.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Impulse, Momentum, and Baseball
  1. Baseballs and impulses (Replies: 2)

  2. Momentum - Baseball (Replies: 7)