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Homework Help: Newton's Second Law Equation acceleration Question

  1. Jul 26, 2012 #1
    1. The problem statement, all variables and given/known data
    A certain force gives object m1 an acceleration of 12.0 m/s2. The same force gives object m2 an acceleration of 3.30 m/s2. What acceleration would the force give to an object whose mass is (a) the difference between m1 and m2 and (b) the sum of m1 and m2.

    2. Relevant equations

    3. The attempt at a solution
    I found these two solutions online:
    but I can't follow their math. I tried manipulating the above equation similarly, to no avail.

    Any help is greatly appreciated!
  2. jcsd
  3. Jul 27, 2012 #2
    Which part that you do not understand.
    Use the formula a=F/m.
  4. Jul 27, 2012 #3


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    Hello Slusho. Welcome to PF !

    What are those manipulations? What have you tried?

    F = m1a1 and F = m2a2, where a1 = 12.0 m/s2 and a2 = 3.30 m/s2 .

    Therefore, [itex]\displaystyle m_1=\frac{F}{a_1}\text{ and } m_2=\frac{F}{a_2}\,.[/itex] Correct?

    Now, use all this with F = (m1 + m2)a1+2 to find a1+2 .

    How's your algebra?
  5. Jul 27, 2012 #4
    I figured it out!

    [tex]\frac{1}{a_{1+2}}=\frac{1}{F}(\frac{F}{a_{1}}+ \frac{F}{a_{2}})[/tex]

    Thank you so much for you help! I had to work it several ways for a good half hour until I did it correctly.
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