A stone is dropped from the top of the well that has water in it at a depth of 30.0 m. How long does it take the stone to reach the water?
I'm assuming that the water surface is 30m below the top of the well......so
-30 = -4.9t^2 divide both sides by -4.9
[ -30 / -4.9 ] = t^2 take the positive root of both sdes
sqrt [ -30 / -4.9] = t ≈ 2.47 sec