The figure shows the force acting on a 2.0 kg object as it moves along the xaxis. The object is at rest at the origin at t= 0 s.
http://session.masteringphysics.com/problemAsset/1…
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,
v=v0+at
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)=65=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