Forces Homework: Finding Work and Velocity

[-Physician]

Homework Statement

We have a body with mass=1kg and it's on rest. When a force of 5N acts on it , the body displaces 4m. Assume no friction
Find:
a)The work that force did
b)Velocity at the end of the distance(displace)
a)
$Work=Force * Displacement = 5N*4m = 20J$
$A=Fd=(5N)(4m)=20J$
b)
Uhm,
$F=\frac{mv}{t}$, i have no time given. My teacher said this has a solution, it's not wrong. I'm stuck here

The Attempt at a Solution

a)
$Work=Force * Displacement = 5N*4m = 20J$
$A=Fd=(5N)(4m)=20J$
b)
Uhm,
$F=\frac{mv}{t}$, i have no time given. My teacher said this has a solution, it's not wrong. I'm stuck here

 

[gneill]

Look for a kinematic formula that relates velocity, acceleration, and distance, since those are the things you have to work with.

 

[-Physician]

Ehm, maybe that would be:
$a=F/m$
$a=5N/1kg=5m/s^2$
$a=\frac{Δ v}{Δ t}$
$5m/s^2=\frac{v_1-0}{t}$
I have no v_1(which i have to find) and I have no time..
If so, would that be
$v^2=v_0^2+2ax$ which gives us
$v^2=0m^2/s^2+2(5m/s^2)(4m)$
$v^2=40m^2/s^2$
$v=\sqrt{40}=6.324555320336759m/s$

 

[gneill]

That works!

 

[-Physician]

thanks!