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Homework Help: Impulse and Momentum of a force on a ball

  1. Feb 25, 2009 #1
    1. The problem statement, all variables and given/known data
    1. The force shown in the figure below is the net eastward force acting on a ball. The force starts rising at t=0.012 s, falls back to zero at t=0.062 s, and reaches a maximum force of 35 N at the peak. Determine with an error no bigger than 25% (high or low) the magnitude of the impulse (in N-s) delivered to the ball. Hint: Do not use J = FΔt. Look at the figure. Find the area of a nearly equally sized triangle. [Figure attached.]

    2. A bat hits a moving baseball. If the bat delivers a net eastward impulse of 0.6 N-s and the ball starts with an initial horizontal velocity of 3.8 m/s to the west and leaves with a 4.2 m/s velocity to the east, what is the mass of the ball (in grams)?

    2. Relevant equations

    3. The attempt at a solution
    1. Since I don't know the equation of the line, I can't take the integral of F(t) from (tf) to (ti). And I don't know at what time F=35 N, so I can't make an accurate estimate of the area underneath the line.

    2. I have no clue where to even begin.

    Attached Files:

  2. jcsd
  3. Feb 26, 2009 #2


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    Homework Helper

    draw a picture of the force with time - you should be able to work out 3 points from the info given...

    the integral of F.dt is effectivley calculating the are under the curve of F against t

    2. impulse = cahnge of momentum write down the equations & what you know
  4. Feb 26, 2009 #3
    1. Got it!

    2. 0.6=4.2m-(-3.8)m and solve for m. Right?
  5. Feb 26, 2009 #4


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    Homework Helper

    looking good to me
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