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An object with mass 5 kg is under constant force (10i+20j)N

  1. Nov 20, 2012 #1
    An object with mass 5 kg is under constant force (10i+20j)N......

    1. The problem statement, all variables and given/known data

    (Question is in the attachment)

    For the question I used the equation F=ma= m Δ(Vf-vi)/t and plugged in 5 for m and for
    velocity I put (vf -(-5+30)/10= (10i + 20j)N. My final equation was

    (10i+20j)N= 5(vf-(-5+30)/10

    This is as far as I got and I can't solve the question =(. Am i doing something wrong?
     

    Attached Files:

  2. jcsd
  3. Nov 20, 2012 #2
    Re: An object with mass 5 kg is under constant force (10i+20j)N......

    Vector [itex]\equiv[/itex] fun with a direction. :tongue2:
    (10i + 20j) = 5([itex]\vec{v}[/itex][itex]_{f}[/itex]-(-5i + 30j))/10

    Simplify...
    (10i + 20j) = (1/2)([itex]\vec{v}[/itex][itex]_{f}[/itex]-(-5i + 30j))

    Multiply vectors by the scalar
    (10i + 20j) = (0.5)[itex]\vec{v}[/itex][itex]_{f}[/itex]-(-[itex]\frac{5}{2}[/itex]i + 15j)

    Adding the "scaled" initial velocity vector to the other side
    (10i + 20j) + (-[itex]\frac{5}{2}[/itex]i + 15j) = (0.5)[itex]\vec{v}[/itex][itex]_{f}[/itex]

    Add vectors by components
    (7.5i + 35j) = (0.5)[itex]\vec{v}[/itex][itex]_{f}[/itex]

    (15i + 70j) = [itex]\vec{v}[/itex][itex]_{f}[/itex]

    That's the third answer I see on the attachment, so I might have done this right.
     
  4. Nov 20, 2012 #3
    Re: An object with mass 5 kg is under constant force (10i+20j)N......

    Thanks a lot man! :D
     
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