A body starts moving with velocity Vo and constant acceleration a. After moving a certain distance, it attains a velocity of V. What is its velocity as it moves half the distance?

Vo = 1m/s
V = 7m/s

Two equations come to mind

(Vf^2 - Vo^2)/2x = a

Rearrange the equation to solve for Vf using your found value of a. I remember when this used to be difficult for me. Heck, it still is. Damn cylindrical coordinates and centripetal motion with Netwon's second law.. *grumble*