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Homework Help: Impulse problem (intro mechanics)

  1. Nov 10, 2009 #1
    1. The problem statement, all variables and given/known data

    A rubber ball (mass 0.26 kg) is dropped from a height of 1.7 m onto the floor. Just after bouncing from the floor, the ball has a speed of 3.6 m/s.
    (a) What is the magnitude and direction of the impulse imparted by the floor to the ball? Magnitude ? kg ยท m/s

    (b) If the average force of the floor on the ball is 17 N, how long is the ball in contact with the floor?

    2. Relevant equations


    3. The attempt at a solution

    a)the unknown is the initial speed of the dropping ball under free fall:

    vi= sqrt (2 x 9.8 x 1.7) = 5.8

    delta p= 0.26 (3.6--5.8)=2.4

    b) dt=dp/Fave=0.14 s

    Please let me know what is wrong here, my electronic assignment system is telling me the numbers are wrong. Thank you!
  2. jcsd
  3. Nov 10, 2009 #2


    User Avatar
    Homework Helper

    Your answers all seem right to me.
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