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Homework Help: Force between two masses

  1. Apr 2, 2012 #1
    1. The problem statement, all variables and given/known data
    Three small children of mass, 20kg (first child),24kg(middle child) and 16kg (third child), respectively, hold hands and are pulled across a smooth frozen pond (which will occur sooner rather than later) by a larger boy on skates. He pulls thm via horizontal rope being held by the first child (20kg). The skater pulls on the rope with a force of 135N. Calculate each of the following :
    -the acceleration of the skater
    -the force with which each pair of children must hold hands to ensure that the chain is not broken.

    2. Relevant equations


    3. The attempt at a solution
    I've solved the first part, which was 2.25, but for some reason i cant seem to get the right answer for the second part (90.0N, 36.0N). I've tried using Fnet=ma for the second part aswell, and haven't thought up anything else. I'm studying for a test, which is why I need to figure out how to do this, any help would be very much appreciated!

    Never mind! i figured it out!
    Last edited: Apr 2, 2012
  2. jcsd
  3. Apr 2, 2012 #2
    What numbers are you using in the F=ma formula?
  4. Apr 2, 2012 #3
    I was adding the 20 and 24 and then multiplying by acceleration. I understand what I was doing wrong now, regardless, thank you for answering so fast!
  5. Apr 2, 2012 #4
    I'm glad you found the right answer.

    You came to the conclusion that you add the 24 and 16 together instead, because those are the masses being accelerated, right?
  6. Apr 2, 2012 #5
    yes I did. Took me longer than I'm proud of though haha. Thanks
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