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Basic Motion Graphs (velocity-time)

  1. Sep 24, 2009 #1
    Momentum & Net Force Question

    Okay, so I got the previous question I asked and I had another new question to ask so rather than make a new topic and seem like I'm spamming the forums, I just decided to edit my original post. I just hope no one replies to my old post while I'm writing this one!

    1. The problem statement, all variables and given/known data
    A ping-pong ball whose mass is 0.0027 kg (2.7 g) is acted upon by the Earth and the air (there is air resistance, and there is also a strong wind). This table gives the position of the ball at several times:
    Time Position

    12.35 s < 3.17, 2.54, -9.38 > m
    12.39 s < 3.25, 2.50, -9.40 > m
    ... ...
    14.35 s < 10.17, -1.16, -10.40 > m
    14.39 s < 10.37, -1.27, -10.42 > m


    In the time interval from 12.35 s to 14.35 s, what was the average net force acting on the ball?

    2. Relevant equations
    Fnet = P/t where p is momentum and t is time interval
    Fnet = -mg

    3. The attempt at a solution

    First I get the displacement by subracting the final position vector - initial position vector. I then divide that vector by the time interval (2 seconds) to get the average velocity. I use the formula p = mv to find the momentum.

    I rearrange the formula p = fnet( t ) to isolate for fnet
    so fnet = p/t.

    However, with this method I do not get the right answer.
     
    Last edited: Sep 24, 2009
  2. jcsd
  3. Sep 24, 2009 #2
    Okay, so I got the previous question I asked and I had another new question to ask so rather than make a new topic and seem like I'm spamming the forums, I just decided to edit my original post. I just hope no one replies to my old post while I'm writing this one!
     
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