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Homework Help: What is the velocity of the body

  1. May 3, 2010 #1
    The only force acting on a 3.4 kg body as it moves along the positive x axis has an x component Fx = - 6x N, where x is in meters. The velocity of the body at x = 3.0 m is 8.0 m/s.

    a) What is the velocity of the body at x = 4.0 m? m/s

    (b) At what positive value of x will the body have a velocity of 5.0 m/s?
    i have some kinda idea but it may not be clear
    so i started with using a Formula for work since its moving along positive x direction
    W=Fd cos(angle)
    and kinetic energy is
    K=1/2mv^2
    thats all i can think off for the beginning
    Plz just give me some hint how to combine these 2 formulas since angle between force and direction is 180 it will be cos180
     
  2. jcsd
  3. May 3, 2010 #2

    rock.freak667

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    Your force is varying with x.

    So if the only force acting is Fx= 6x, can you use Newton's second law to find an expression for velocity?

    (Hint: dv/dt = dv/dx * dx/dt)
     
  4. May 3, 2010 #3
    still dont get it
     
  5. May 3, 2010 #4

    rock.freak667

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    F= ma

    -6x = ma
     
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