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

out experiencing an acceleration bigger than5g. 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?