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Homework Help: Force vs Time Graph

  1. Oct 11, 2005 #1
    A 2.0kg object initially at rest at the origin is subjected to a time-varied force. What is the objects velocity at 4 seconds?

    The Graph
    For the first two seconds there is a force of 6.0N. The the force decreases linearaly to 0N at 4 seconds. How do I find the velocity of the object at 4.0 seconds?

    I got the velocity at 2 seconds by using F=ma and solving for a:

    6.0=2.0a
    a=3

    With that acceleration I then found:

    V=Vi+at
    V=0+(3)(2)
    V=6

    I just don't know how to get the rest.
     
  2. jcsd
  3. Oct 11, 2005 #2
    Hello? Anyone out there?:smile:
     
  4. Oct 11, 2005 #3

    Fermat

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    Homework Helper

    Use F=ma again.

    But this time F is a function of time, so the eqn becomes,

    F(t) = ma

    However, in this case, it is a fairly simple application. The accelerating force is decreasing linearly, so all you have to do is just take the average value of F, over the last 2 secs, in place of F(t).:smile:
     
  5. Oct 11, 2005 #4
    Thanks buddy!
     
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