Velocity of 2.0kg Object at 4s: Solving Force vs Time Graph

[godplayer]

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.

 

[godplayer]

Hello? Anyone out there?

 

[Fermat]

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).

 

[godplayer]

Thanks buddy!