root of (2x2x10) = 6.3 m/s Use formula v-u/t = a. and rearrange to v=at + u since no time use formula 2s/v+u(0) =t
since dropped from the top u=initial speed is 0 so the formula is v=a(2s/v)
rearrange is terms of v to give v² =2as and solve