What is its velocity at t=6s?

NetherCraft 0

The figure shows the force acting on a 2.0 kg object as it moves along the x-axis. The object is at rest at the origin at t= 0 s.


I know the acceleration is 0 but im having trouble with the velocity.

thats wrong.

2 Answers

  • Since F=ma we can get acceleration on the object by a=F/m

    From t=0 sec to t=3 sec, a=4/2=2 m/s^2

    From t=3 sec to t=5 sec, a=-2/2=-1 m/s^2

    From t=5 sec on, a=0 m/s^2

    Use velocity from constant acceleration equation,


    break it down into the chunks where the acceleration changes, use the final velocity at that time, as the inital velocity for the next acceleration.

    At t=0, v=0, at t=3, v=0+2*(3)=6 m/sec

    At t=5 sec, v=6+(-1)(5)=6-5=1 m/sec

  • Let’s work this in parts…

    part 1 time 0 to 3 seconds

    F = m * a then a = 4/2= 2 m/s^2

    Vf = Vo + at therefore Vf= 2*3 = 6 since Vo =0

    part 2 3 to 5 seconds

    vf last part is Vo on this part

    Vo = 6

    a = – 1

    t= 2

    Vf = Vo + at

    Vf = 6 – 2 = 4

    last part

    5 to 6 seconds

    Vo = 4 last vf is Vo on this part

    t = 1

    a= 0 there is no force

    Vf = Vo + at

    Vf = 4

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