i)A boy of 45kg is 5m above a swimming pool on a spring board. The boy jumps up into the air which is 2m above the spring board before falling into the water. What is the maximum depth the boy can reach in the water if the average resisting force of water on the boy is 1500N?

ii) Calculate the boy's deceleration when he is sinking in the water.

I do not know how to calculate the depth he can reach and his deceleration in the water.

his energy (gravitational) is

... m g (h+d) = 45 * 9.8 * (7+d)

the depth (d) he reaches is based on the work done by the water
... w = f d = 1500 d

1500 d = 45 * 9.8 * (7+d)

f = m a ... a = f / m
his deceleration is the net force (gravity minus water) divided by his mass
a = [(m g) - 1500] / 45