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Homework Help: Atwood machine

  1. Nov 8, 2008 #1
    1. The problem statement, all variables and given/known data
    In the Atwood machine shown below, m1 = 2.00 kg and m2 = 7.50 kg. The masses of the pulley and string are negligible by comparison. The pulley turns without friction and the string does not stretch. The lighter object is released with a sharp push that sets it into motion at vi = 2.80 m/s downward.
    (a) How far will m1 descend below its initial level?

    (b) Find the velocity of m1 after 1.80 s.

    2. Relevant equations
    f= ma
    vf^2 = v^2 + 2ad

    3. The attempt at a solution
    i think for part a u use the equation i put above..but i dont know how to figure out acceleration...but i think its splitted between the two objects
  2. jcsd
  3. Nov 9, 2008 #2


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    Homework Helper

    Hi physics_geek,

    To find the acceleration, start by drawing force diagrams for each of the objects. Using [itex]\sum F = m a[/itex] for each of the diagrams then gives two equations with two unknowns.

    (You can also use an energy appoach here.)
  4. Oct 19, 2011 #3
    Use the formula a= (gm1 + gm2)/(m2+m1) to find the acceleration then use the formula V^2=-2ad to find the distance. Bada bing bada boom!
    Im still workin on the second part unfortunately...
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