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Help Needed! Deceleration! Quick Please!

  1. Jun 3, 2009 #1
    1. I need to find the deceleration of a bicycle, I have Finial velocity at 0, initial velocity at 5.56m/s and discplacement at 1.80m



    2. V^2+U^2/(2*S)=A
    not sure if formula is correct



    3. The attempt at a solution
    I find that 0^2+5.56^2/(2*180) = -27m/s/s
    Is this correct? i think its too fast
     
  2. jcsd
  3. Jun 3, 2009 #2

    Doc Al

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    Staff: Mentor

    Redo your arithmetic.
     
  4. Jun 3, 2009 #3
    (v^2-u^2)/(2*s)=a

    (0^2-5.56^2)/(2*1.8m) = -27m/s/s

    ... is that better?
    Is the formula incorrect?
     
  5. Jun 3, 2009 #4

    tiny-tim

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    Science Advisor
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    Welcome to PF!

    Hi Masschaos! Welcome to PF! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    Your formula (a = -u2/2s) is correct, but your arithmetic isn't …

    did you multiply by 1.8 instead of dividing? :confused:

    (you don't seem very good at using brackets)
     
  6. Jun 3, 2009 #5
    Thanks! its late at night here and i was stressing because i thought i had the wrong formula for my assignment... thanks for the heads up

    So what i should do is (v2-u2)/2*1.8)?
     
  7. Jun 3, 2009 #6

    Doc Al

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    Staff: Mentor

    Yes. The formula is a = (v2 - u2)/(2*s), not ((v2 - u2)/2)*s (which is what you seemed to be doing). I suspect you are just being sloppy with your calculator.
     
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