This is more of a physics problem. The diver is in free fall. And gravity is pulling him down at 9.8m/s^2. If his initial velocity was 0 we can find out his final velocity at 40 seconds by multiplying 9.8 by 40. Then we can find the distance he travelled by taking the final velocity and adding it to the initial velocity dividing by 0 and multiplying by time at 40 seconds.