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Intro physics dynamics

  1. Oct 13, 2009 #1
    I have posted a problem below and my attempt could someone please tell me if I am going wrong and where. Thanks

    An automobile of mass 650 kg is acted on by a net force (F) given by F = 800 - 40.0t, where t is in seconds and F is in Newtons. At t=0, the velocity of the automobile is 5.00m/s.

    a) Find the acceleration of the automobile at t=10.0s

    800-40(t) / 650 = 400/650 = .615 m/s^2

    b) Find the velocity of the automobile at t=10.0s

    .615t = .615(10s) =6.15 m/s

    c) Find the distance covered in this time.

    x = (1/2)V*t
    (1/2)(6.15)(10) = 30.75 m

    d) At what time will the automobile be moving with a velocity of 15.0 m/s

    V=at

    t=V/a = 15/.615
    t= 24 s
     
  2. jcsd
  3. Oct 13, 2009 #2

    Suy

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    b is incorrect
    remember a=(final velocity-initial velocity)/ (delta time)
     
  4. Oct 13, 2009 #3
    In this problem there is no final velocity?
     
    Last edited: Oct 13, 2009
  5. Oct 13, 2009 #4

    Suy

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    At t=0, the velocity of the automobile is 5.00m/s.
    For B, you are solving the final velocity at 10.0s, (initial is not 0)
     
  6. Oct 13, 2009 #5
    ok correct me if I am wrong..I am a beginner at this..

    So if I rearrange the equation you gave me

    final velocity = initial velocity + acceleration * time
    = 5.00 + (.615 * 10.0 )
    = 11.15 m/s ????
     
  7. Oct 13, 2009 #6

    Suy

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    Correct
     
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