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Homework Help: Force problem

  1. Sep 25, 2012 #1
    1. The problem statement, all variables and given/known data

    A tennis racket (950 g) hits a tennis ball (110 g) with a force of 5000 N. What is the acceleration of the tennis ball? During the collision, with what force does the tennis ball hit the tennis racket? What is the acceleration of the tennis racket? (Remember that force and acceleration are vectors, so be careful with positive and negative signs. Assume the player lets go of the racket just after contact.)

    2. Relevant equations

    f = m*a
    3. The attempt at a solution
    a) 45.4 m/s2
    b) -5000 N
    c) 5000=950a
    -5.3 m/s2
  2. jcsd
  3. Sep 26, 2012 #2
    Hi Meowserkitty
    Be careful with your units, 1N=1Kg/s²
  4. Sep 26, 2012 #3
    Nope, 1N=(1kg(m))/s2
    Also, whenever you see collisons, that just begs momentum. (p=mv)
    Your answer was way too simplistic. Physics is (almost) never that easy, unfortunately.
  5. Sep 26, 2012 #4
    Ah yes, sorry I forgot the m because I was looking at putting the bold tag around Kg first :)
  6. Sep 26, 2012 #5
    Could you explain how I should go about this? Our physics teacher was gone all week and could not help us.
  7. Sep 26, 2012 #6
    You just have to transform the mass expressed in g as expressed in Kg, that is, you divide it by 1000 :)
  8. Sep 26, 2012 #7
    Other than that do I do the same thing I did? And would the rackets acceleration be negative?
  9. Sep 26, 2012 #8
    We are not doing momentum yet
  10. Sep 26, 2012 #9
    Yes, you are :)
    Maybe you didn't call it this way in class, but the Newton's law you are using is
    "the force is the rate of change of momentum"
    As far as you are/will be concerned for a while, mass is constant, so that becomes
    F=mdv/dt=ma :)
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