Solving Force vs Time Graphs: Velocity Example #37

[kk727]

Homework Statement

I was given this worksheet today:
http://www.mrwaynesclass.com/impulse/WS/momentum.pdf

However, I was not in school today nor when we started momentum. So I'm a little confused with the graphs. On a force versus time graph, how do you go about solving for velocity? An example problem would be #37. They give you the answer to be -1 m/s (answers are at the bottom) but how do you get there?

Homework Equations

P=mv
ΔP/ΔT = F
F=ma

The Attempt at a Solution

I figured that impulse (ΔP) would be area under the curve, so I calculated that. But using the force and time on the graph, the impulse didn't match up and I just got all confused and frustrated. Can anyone help?

 

[kk727]

I just realized that the worksheet has two problems that are #37... -_- So I'm doubting that -1 m/s is the answer to this one. I'm still confused with trying to solve it, though!

 

[iRaid]

I just realized that the worksheet has two problems that are #37... -_- So I'm doubting that -1 m/s is the answer to this one. I'm still confused with trying to solve it, though!

There is no way it's -1...
Try doing this:
Using F=ma, you can get the acceleration, right? With the acceleration you can use the kinematics equations to get the answer.

You have:
Vi = 0
Acceleration = You find it
Time = 20 s
Vf = ? (solve)

So you can use:
vf = vi + at