What is the final velocity from given work, mass, initial velocity, and time?

[cretin66]

Homework Statement

I am trying to find the final velocity from the given data
Work - 3000J
Mass - 1/2d (d = distance travelled)
Initial Velocity - 7m/s
Time - 7 seconds

Homework Equations

W=change in energy
W=Fd

The Attempt at a Solution

W =work
F=force
m=mass
a=acceleration
d=distance traveled
vf= final velocity
v0=initial velocity
t=time
Attempt #1
W=Fd
W=mad
3000=1/2d[2]a
W=1/2(vf + v0/2t)[2](vf - v0/t)
and by solving this equation...
vf[3] + 7vf[2] - 49vf - 343 = 3000
I've tried putting everything equal to zero and using a graphing calculator to solve for the x-intercept, and using a check i found that i had the wrong answer, it's possible that my algebra was done improperly, or I am approaching the problem the wrong way, please help.
The answer i got was vf = 230.84

 

[olivermsun]

W=1/2(vf + v0/2t)[2](vf - v0/t)

How did you get this equation?

 

[cretin66]

because d=vf + v0/2/t, i just replaced all the d's in the equation with this value

 

[olivermsun]

I guess I'm having a little bit of confusion with your symbols. [2] is squared, and m = 1/2d = d/2 or is it 1/(2d)?

 

[cretin66]

1/2d=d/2, sorry I was in a hurry, and yes [2] is squared