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working out acceleration when given speed and distance watch

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    v= 17.5 ms-1
    u= 0 ms-1
    s = .20m


    v^2=u^2+2as
    v=u+2as
    0=17.5+2*(a*.20)
    -17.5=2*(a*.20)
    8.75=a*.20
    43.75=a



    am i on the right lines
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    How did you lose your squares in:

    v^2=u^2+2as

    to

    v=u+2as?

    As a general note though, you're trying to find a, so rearrange the formula to be for a BEFORE putting any numbers in, it will make your life easier. You're putting the numbers in, then sorting it out.
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    (Original post by JoMo1)
    How did you lose your squares in:

    v^2=u^2+2as

    to

    v=u+2as?

    As a general note though, you're trying to find a, so rearrange the formula to be for a BEFORE putting any numbers in, it will make your life easier. You're putting the numbers in, then sorting it out.
    thanks for that, i realised after i posted it i should now have taken away the squares i did that cos i saw them on both side but realised it is v^2 and u^2 so would not be right to cancel them out
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    (Original post by Foster88)
    thanks for that, i realised after i posted it i should now have taken away the squares i did that cos i saw them on both side but realised it is v^2 and u^2 so would not be right to cancel them out
    That would be fine, but you'd need to sqrt the 2as
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    v^2=u^2+2as

    v^2/u^2-2s=a

    a= 0.4

    hmm still seems wrong ? :/
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    v^2=u^2+2as
    2as=v^2-u^2
    a=(v^2-u^2)/2s
    Then input the numbers. Try practicing more rearrangments, or deriving the other constant acceleration equations to get more comfortable with it.
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    (Original post by vandub)
    v^2=u^2+2as
    2as=v^2-u^2
    a=(v^2-u^2)/2s
    Then input the numbers. Try practicing more rearrangments, or deriving the other constant acceleration equations to get more comfortable with it.
    wouldnt this give 0 as an answer though :/

    i think i get it now sorry
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    (Original post by Foster88)
    wouldnt this give 0 as an answer though :/
    Nope.
    a=(v^2-u^2)/2s
    =17.5^2/(2*.2)
    =306.25/.4
    =765.625 ms^2
    Why did you think it'd give 0?
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    (Original post by vandub)
    Nope.
    a=(v^2-u^2)/2s
    =17.5^2/(2*.2)
    =306.25/.4
    =765.625 ms^2
    Why did you think it'd give 0?
    why i tried arranging the equations i was dividing the u^2 instead of minus(ing) it my bad
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    (Original post by Foster88)
    why i tried arranging the equations i was dividing the u^2 instead of minus(ing) it my bad
    Ah right. Although, you should know that dividing by 0 doesn't equal zero, instead it's undefined, as in, there is no answer, so it can't be done.
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    [QUOTE=Foster88;30862711]v= 17.5 ms-1
    u= 0 ms-1
    s = .20m


    v^2=u^2+2as
    v=u+2as
    0=17.5+2*(a*.20)
    -17.5=2*(a*.20)
    8.75=a*.20
    43.75=a

    Are you sure s=0.2m?
 
 
 
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