Initially body is at rest , hence initial velocity is Zero .
Acceleration = 5 m /s^2
Distance traveled = 50 meters.
We Know that
V² - U² = 2as
Where V = final velocity ,
U = initial velocity
a = Acceleration of the body
s= Distance Covered
V² - 0² = 2*5*50
V² = 500
V = √(500)
V = 10√5
Hence the Final Velocity of the body is 10√5.