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 Question

  1. Jul 16, 2006 #1
    i drew a digram for the forces and i found out the equations for accerleration... then i'm stuck...

    Question: Determine the tension in the strings, the acceleration, and how far the masses will go in 2.0s. (See attachement)

    Well i drew a FBD, ,and i got three eqations for accerleration:
    for mass 1 (100g):
    A = (T2 - M1*G)/(M1)
    A = (T2 - 0.1*9.8)/(0.1)

    mass 2: (200g, on the floor)
    A = (T1 - T2)/(M2)
    A = (T1 - T2)/(0.2)

    mass 3: (200g, going down on the right)
    A = (M3*G - T1)/(M3)
    A = (0.2*9.8 - T1)/(0.2)

    Then what should i do after this? i can't equate 3 equations at once... can i?

    Attached Files:

  2. jcsd
  3. Jul 16, 2006 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Why not? After all, if the string does not break the accelerations are all the same. Try inserting the expressions for T1 and T2 from equations 1 and 3 into 2. That will give you an equation with only one unknown: A.

  4. Jul 17, 2006 #3
    yea i tried that, but a strange number came out... i will try again, maybe it's a algebra error.
  5. Jul 17, 2006 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Your equations look right. Did you solve for both tensions and for the acceleration? If so, there is an easu way to tell if you made an algebra mistake: just plug back your values in the initial equations! If it does not work, it shows that you made an algebra mistake.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook