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Homework Help: Could someone please help me out ? grade 11 physics ?

  1. Feb 9, 2015 #1


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    • Member warned: Non-Descriptive Thread Title
    1. The problem statement, all variables and given/known data
    A 2 kg sponge is dropped from rest, pulled down by gravity. how fast will it be travelling in 6 seconds, with a 5 N force of air resistance acting on it ?

    2. Relevant equations
    vf= vi+ gt (im just guessing coz im not sure )

    3. The attempt at a solution
    the speed in 6 seconds ?? (im not sure what to write here)

    so could someone please help me out pleaseeee???? thank you!!!!!!!!!
  2. jcsd
  3. Feb 9, 2015 #2


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  4. Feb 10, 2015 #3


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    Welcome to PF!

    The wording of the problem is not clear, did you copied it correctly? Was it not "how fast will it be travelling in the 6th second" ?
    Anyway, it is said that also air resistance acts on it, in addition to gravity. So what is the acceleration of the sponge? vf=vi+gt is valid when the only force is gravity.
  5. Feb 10, 2015 #4
    First, find the acceleration using the Second Newton Law
    Then, use the formula vf= vi + at to get the final velocity (Note : Use negative sign for the opposite direction of the falling ball)
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