From a platform tower 10 m high, a diver performs a handstand dive.

His height, h, in metres above the water at t seconds can be modelled by

h(t) = 10 - 4.9t^2. Estimate the rate at which the diver enters the water.

The answer is supposed to be -14m/s i just don't understand how to get to that answer. At first a solution seemed simple, but i got the wrong answer.

Thanks in advanced, Joe