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Homework Help: Combining Newton's Laws and Kinematic

  1. Dec 3, 2016 #1
    1. The problem statement, all variables and given/known data

    Max (65 kg) pushes Toni (50 kg) with a force of 360 N. The force of friction is 0 on Toni and 80 on Max.
    (a) Find each girls acceleration
    (b) If Max pushes Toni for 0.1 s, how far will Toni travel in 0.5 s?
    2. Relevant equations

    3. The attempt at a solution
    For (a), I got the correct answers by using Fnet=ma
    Max's acceleration:4.3m/s^2 (left)
    Toni's acceleration: 7.2m/s^2 (right)
    For (b), Toni's acceleration is only 7.2 during the 0.1 seconds so...
    To find the distance for the remaining 0.4 seconds, I need to find v1 which is v2 of the 0.1 seconds
    v2=0.72 m/s
    So v1 for the 0.4 s is 0.72. I assumed acceleration is 0 during this time and that she is now moving at a constant velocity
    It's very close to the answer my teacher gave which is 0.33 m..but I'm just curious as to why it's a little off because it might be considered wrong on a test.
  2. jcsd
  3. Dec 3, 2016 #2


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    Science Advisor
    Homework Helper
    Gold Member

    It's off probably because of round off errors. Carry the intermediate calculations to more decimal places and see what happens. Better yet, derive a symbolic answer and substitute the given quantities at the very end.

    On edit: I ran the numbers and got 0.324 m. If you are concerned about this, you may consider asking your teacher.
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