Physics problem on final speed?

Question

Hi I need help understanding this problem :

You are stranded in space away from your spaceship, no force acting on you so you are completely motionless . Suddenly you remember you have a propulsion unit that provides a constant force of 34N, you turn it on. After some time you have moved a distance of 2.25m. Assume you weigh, 68kg. What is your final speed?

Answer 1

 

 

The force is constant, so is the acceleration:

 

a=F/m=0.5(m/s)

 

and, the speed is varied during time as,

 

V=a*t

 

let's find "t" - time.

 

The distance is,

 

S=at^2/2  , so  t=(2S/a)^0.5

 

Thus,  V=a*t=(2a*S)^0.5=(2.25)^0.5=1.5(m/s)