# Forces - Homework

1. Mar 6, 2012

### -Physician

1. The problem statement, all variables and given/known data
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

3. 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

2. Mar 6, 2012

### Staff: Mentor

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

3. Mar 6, 2012

### -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
$v^2=0m^2/s^2+2(5m/s^2)(4m)$
$v^2=40m^2/s^2$
$v=\sqrt{40}=6.324555320336759m/s$

4. Mar 6, 2012

That works!

5. Mar 6, 2012

thanks!