i obtained the degree in Chemical engineering in 1976, i worked some years in Industry, and i have teached Chemistry, Physical Chemistry, and Industrial Chemical Technologies (and other subjects) since 1982
like i said, the movement of fall is connected with aceleration with the relation : y = 1/2 gt^2 with g = gravity aceleration and not with y= gt^2. If the text give this relation I suppose a= 1/2 g . If you conseder g of the text the gravity aceleration you obtain 10 m/s but it is wrong
With what speed does the rock hit the bottom?