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Homework Help: Constant force of ball

  1. Jan 3, 2008 #1
    1. The problem statement, all variables and given/known data
    A 5.00 kg ball strikes a wall with a velocity of 6.0 m/s to the left. The ball bounces off with a velocity of 5.0 m/s to the right. If the ball is in contact with the wall for 0.30 s, what is the constant force exerted on the ball by the wall?



    2. Relevant equations

    f=p/t

    3. The attempt at a solution

    Ok so i found p which i did mv or (5)(11) then plugged it to p/t and did 55/0.30 and got 183.3 N to the right...is that correct?

    Thanks!
     
  2. jcsd
  3. Jan 3, 2008 #2

    rock.freak667

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    Initial momentum is 5*-6=-30 kgms^-1

    Final momentum is 5*+5=+25kgms^-1

    what is the change in momentum? how does newton's 2nd law apply?
     
  4. Jan 3, 2008 #3
    oh....so 5 **Net force on an object is equal to its rate change of momentum.
     
  5. Jan 3, 2008 #4
    but that's such a small number is that possible??
     
  6. Jan 3, 2008 #5

    rock.freak667

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    Yes


    The change in momentum=Final-Initial=25-(-30)=55kgms^-1

    and by newton's 2nd law:F=55/0.3

    so you are correct.
     
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