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Two blocks are pulled across a frictionless surface by a $240\ N$ force, as shown in the diagram below: $60\ kg$ - - - cord - - - $20\ kg$ → $240\ N$. If the blocks are accelerating at $3\ m/s^2$ what is the tension of the cord in between the two blocks? So I don't really have a strategic approach to this problem. I Isolate $20\ kg$ and see that $f = (20\ kg)(3\ m/s^2)$. Therefor it takes 60 newtons for that block to accelerate at $3\ m/s^2$ and the other 180 newtons are used to pull the second block and therefor $180\ N$ is the tension.

  1. Is that correct, my teacher never gives me the answer sheet :(
  2. Is there a step by step approach I can apply to tension questions?

Thanks a lot!

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migrated from math.stackexchange.com Sep 29 '11 at 3:08

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closed as off topic by dmckee Sep 30 '11 at 1:30

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Yes, that's correct. Another way to see this is that it takes 180 N to accelerate the 60 kg body at 3 m/s², and the only place that force can come from is the tension in the cord. –  Rahul Sep 28 '11 at 21:31
@joriki: You're right, but when I attempt to migrate this question to physics.SE it doesn't seem to work. I'll leave it open for now, and I've created a meta thread about this problem. –  Zev Chonoles Sep 28 '11 at 21:48
Welcome to Physics.SE! Alas this question was not well migrated as our FAQ states that we do not work elementary exercises qua elementary exercises. We do address question about basic concepts (we even have a meta question to help). That said you are bang on. –  dmckee Sep 30 '11 at 1:33