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Impulse with snowballs hitting a wall

  1. Nov 16, 2016 #1
    1. The problem statement, all variables and given/known data
    Two average forces. A steady stream of 0.250 kg snowballs is shot perpendicularly into a wall at a speed of . Each ball sticks to the wall. Figure 9-49 gives the magnitude F of the force on the wall as a function of time t for two of the snowball impacts. Impacts occur with a repetition time interval , last a duration time interval , and produce isosceles triangles on the graph, with each impact reaching a force maximum . During each impact, what are the magnitudes of (a) the impulse and (b) the average force on the wall? (c) During a time interval of many impacts, what is the magnitude of the average force on the wall?

    2. Relevant equations

    3. The attempt at a solution
    J=Δp=0-.25kg*4m/s= -1 kgm/s
    The impulse should be positive since its asking for the impulse on the wall and not the snow ball correct? I should have had
    .25kg*4m/s-0= 1 kgm/s ?
    Since the graph is of isosceles triangles I can just divide the max F by 2 to get 200N/2=100N
    Or use:
    =100 N
    should just be the maximum force divided by the time interval between the peak of two impacts?
  2. jcsd
  3. Nov 16, 2016 #2
    For c:
  4. Nov 16, 2016 #3


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    Apart from the mass of a snowball, you did not state any input numbers. I deduce you were told the impact velocity, the impact duration, the impact separation, and, redundantly, the peak force. As far as I can tell, your working is all correct.
  5. Nov 16, 2016 #4
    I should have looked at how the copy/paste had actually performed when posting the problem
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