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Homework Help: Average force exerted on ball by wall at angle

  1. Nov 26, 2007 #1
    1. The problem statement, all variables and given/known data

    a 8kg steel ball strikes a wall with a speed of 11.7 m/s at an angle of 35.3 degrees with the normal to the wall. it bounces off with the same speed and angle as shown in the picture.

    http://img405.imageshack.us/img405/7733/asdfkf7.jpg [Broken]

    If the ball is in contact with the wall for 0.297 seconds, what is the magnitude of the average force exerted on the ball by the wall? Answer in N

    2. Relevant equations

    3. The attempt at a solution

    Ft = mv
    F(0.297) = 8 * 11.7
    F = 315.15 kg* m/s^2 or N but thats if its a linear problem

    Angle wise

    Horizontal speed of 11.7 m/s
    Cos 35.3 = x / 11.7
    x = 9.549 m/s

    Extra info
    Vertical speed of 11.7 m/s
    sin 35.3 = y / 11.7
    y = 6.761 m/s

    Ft = mv
    F(0.297) = 8 * 9.549 m/s
    F = 257.2069 N

    is that right?
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Nov 26, 2007 #2


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    Staff Emeritus
    Science Advisor

    Be careful here. Note that in the y direction, the y-component of velocity does not change. On the other hand, the x-component of velocity does change, in direction, but not in magnitude. The magnitudes in the x- and y- directions are correct.
  4. Nov 26, 2007 #3
    Does it matter if I include the y direction in the equation? Would I need to make two equations one going toward the wall and another going away? But then if I equal to them wouldn't it be zero?
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