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Find velocity given F(t)

  1. Oct 26, 2009 #1
    1. The problem statement, all variables and given/known data

    A force of F(t) = t is pushing a block of 5kg mass with no friction. What is the velocity after 10 seconds?

    2. Relevant equations

    F=ma

    3. The attempt at a solution


    F(10) = 10 N

    a = F/m = 10/5 = 2 m/s^2

    a = dv/dt

    v(t) = 2t

    v(10) = 20 m/s


    I've calculated the acceleration by plugging in the time into F(t) and integrated the acceleration to find v(t). But when I plug in the time again into v(t), is that the right step?
     
  2. jcsd
  3. Oct 26, 2009 #2

    ehild

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    The acceleration is not constant, 2m/s2. If the force depends on t so does the acceleration, as it is a=F/m.

    ehild
     
  4. Oct 26, 2009 #3
    So I should carry the t in the force and set a(t) = F(t) / m ?
    a(t) = t / 5

    v(t) = t^2 / 10
    v(10) = 10 m/s?
     
  5. Oct 26, 2009 #4

    ehild

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    Supposing that the block had 0 velocity at the beginning, your result is correct.

    ehild
     
  6. Oct 26, 2009 #5
    ahh thank you
     
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