can i do this using postion vectors?

A jet pilot diving vertically down at 600 km/hr wants to make a quarter turn with-

out experiencing an acceleration bigger than

5*g. At what minimum height must the turn*

begin? Assume that the speed is constant and that after the quarter turn the plane, moving

horizontally, is at ground level.

The solution just quotes a=v^2/R where R is radius of the turn.

I wondered if could start with r(t)=f(t)i+g(t)j for suitable f,g and then differentiate to find acceleration and so do question?