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AP Physics homework problem

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  1. Aug 7, 2012 #1
    1. The problem statement, all variables and given/known data
    Ts (subscript s) = 2∏*√(4.5*10^-2 kg / 2.0*10^3 kg/s^2)
    kg = Kilograms
    s = seconds
    Ts = ?

    2. Relevant equations
    I do not have any relevant questions.


    3. The attempt at a solution
    Ts = 2∏*√(4.5*10^-2 kg)/√(2.0*10^3 kg/s^2) Simplified
    Ts = 6.28*[(0.212 kg)/√(44.72 kg/s^2)] Simplified
    I am not sure what to do past this step. I don't think i could cancel out the kg because I would have only s^2 on the bottom. I have never seen a unit like kg/s^2, so I am confused. Does that unit even make sense? Any help is appreciated.
     
  2. jcsd
  3. Aug 7, 2012 #2

    CWatters

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    You are on the right lines. Consider this bit..

    4.5*10^-2 kg / 2.0*10^3 kg/s^2

    You have kg top and bottom so they cancel giving

    4.5*10^-2 / 2.0*10^3 /s^2

    Then multiply top and bottom by s^2 giving

    s^2 (4.5*10^-2 / 2.0*10^3)

    Now put that back into your equation giving...

    Ts = 2∏*√( s^2 (4.5*10^-2 / 2.0*10^3))

    What does √(s^2) equal?

    See the dimensions work out just fine.
     
  4. Aug 7, 2012 #3
    Oh I think I understand now, so would Ts = 2(pi)*sqrt(0.005)s^2 = 2(pi)*0.0707s = 0.443s?
     
  5. Aug 7, 2012 #4

    CWatters

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    I think you have done sqrt twice by mistake.
     
  6. Aug 7, 2012 #5
    Oh, I just saw that. Thanks. So 2(pi)*(0.005)s^2?
     
  7. Aug 8, 2012 #6

    CWatters

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    No now you forgot to sqrt the s^2 part

    Ts= 2(pi)*(0.005)s
     
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