A ball rolls of the top of stairway with a horizontal speed of 1.5m\s. The steps are 0.5 metre high and 0.5 metre wide. Which step will the ball hit first?

ok, horizontal distance=1.5*time to drop

time to drop=sqrt(2*n*.5/g)
but horizontal distance=.5*n
where n is the step
.5n=1.5*sqrt(2n*.5/g)
solve for n (square both sides
.25n^2=2.25*n/9.8
n=9/9.8
n less than one, so first step it hits.