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Homework Help: Finding ratio of 2 masses with acceleration

  1. Mar 22, 2009 #1
    1. The problem statement, all variables and given/known data
    A force F applied to an object of mass m1 produces an acceleration of 3.00 m/s2. The same force applied to a second object of mass m2 produces an acceleration of 1.30 m/s2.

    Find the ration of m1/m2

    If m1 and m2 are combined, find their acceleration under the action of the force F.

    2. Relevant equations

    3. The attempt at a solution
    for the first part i just used F=m1x3 and F=m2x1.3 and put them together like m1x3=m2x1.3 and used 3/1.3 but that didnt work
  2. jcsd
  3. Mar 22, 2009 #2
    it would be 1.3/3 no 3/1.3 because if you have m1(3)=m2(1.3) then you divide by m2 and have m1(3)/m2=1.3 then divide by 3 and get m1/m2=1.3/3
  4. Mar 22, 2009 #3
    ah stupid mistake on my part, got any ideas on the second part?
  5. Mar 23, 2009 #4
    F = m1 a1
    F = m2 a2

    F/a1 = m1 and F/a2 = m2

    F = (m1 + m2) x, x be the acceleration of the combined mass
    x = F / (m1 + m2)

    x = F / (F/a1 + F/a2)

    x = 1 / (1/a1 + 1/a2)

    x = a1.a2 / (a1 + a2)
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