Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Atwood's Machine Question

  1. Nov 13, 2005 #1
    I dislike simply having answers told to me, so I won't give the actual number values of the question. However, I need some insight on how I would solve this:

    There are two masses on an atwood's machine, but only one of the masses is known (let's say 5 kilograms). I am told that the unknown mass is greater than the known mass, and that the system is accelerating at 2 m/s^2. I am also told that friction is negligible, and to assume that the string is weightless. How would I solve for the unknown mass?

    I think it came to me:
    2(5) + 2(x) = 9.81(x) -9.81(5)
    2(5) + 9.81(5) = 9.81(x) - 2(x)
    10 + 49.05 = 7.81(x)
    59.05/7.81 = (x) = 7.56kg

    Is that right?
    Last edited: Nov 13, 2005
  2. jcsd
  3. Nov 13, 2005 #2
    Yup! You've got it.:wink:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook