Electrostatics uniform electric field of magnitude

[meme177]

An electron with speed 2.00×10^7m/s is traveling parallel to a uniform electric field of magnitude 1.16×10^4N/C .

#1). How far will the electron travel before it stops?
f=ma=Eq=-eE
a=-eE/m
I got a=-2.81x10^15
Then I used v(f)^2=v(i)^2+2a(x-x(i))
Solved for x...
x=-(V(i))^2/2(a)
x=.0712m

#2). How much time will elapse before it returns to its starting point?
v=v(i) +at
If we want the time BEFORE it returns
t=2V(i)/a
t=1.42x10^-8 s

I got both wrong on Mastering Physics ... Please help I don't know what I am doing wrong

 

[haruspex]

An electron with speed 2.00×10^7m/s is traveling parallel to a uniform electric field of magnitude 1.16×10^4N/C .

#1). How far will the electron travel before it stops?
f=ma=Eq=-eE
a=-eE/m
I got a=-2.81x10^15

You appear to have used a field of 1.6E4 instead of 1.16E4.

 

[meme177]

!
I got threw off with all the sixes! Thanx a bunch!