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Find velocity using Force -time graph

  1. Feb 24, 2015 #1
    1. The problem statement, all variables and given/known data
    upload_2015-2-25_0-32-46.png
    The variation of the force F with the time t acting on a body of mass 200g is as shown in the graph below
    Given that the velocity of the body at t=75ms is 15m/s . What is the velocity of the body at t=150ms
    A.15m/s
    B.30m/s
    C.35m/s
    D.39m/s
    2. Relevant equations
    F = m Δv/Δt

    3. The attempt at a solution
    so i calculate the area of ABCDE , and it equal the change of momentum from 75ms to 150ms
    the i calculate the momentum of the body in t = 75ms using v = 15m/s and mass of 200g
    => momentum of the body in t = 150ms => v
    however i dont get any answer in the choices . please tell me where i was wrong
     

    Attached Files:

  2. jcsd
  3. Feb 24, 2015 #2

    Orodruin

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    It will be easier to know where you go wrong if you provide your actual computations rather than describing them in words. The general idea is correct.
     
  4. Feb 24, 2015 #3

    Quantum Defect

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    v = v_0 + integral [dt*F/m]

    Units matter. The area of the first bit (75 ms - 100 ms): [ 70 N * 25 x 10^-3 sec / 200 x 10^-3 kg -- factors of 10^-3 cancel = 8.75 m/s]
     
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