-- Before Adrian left the airplane, his gravitational potential energy was
(mass) x (gravity) x (height) = (80kg) x (9.81m/s²) x (1,000m) = 784,800 joules
-- When he reached the ground, his kinetic energy was
(1/2) x (mass) x (speed)² = (40kg) x (5m/s)² = 1,000 joules
-- Between the airplane and the ground, the Adrian lost
(784,800 joules) - (1,000 joules) = 783,800 joules
Where did all that energy go ?
Energy never just disappears. If it's missing, it had to go somewhere.
The Adrian used 783,800 joules of energy to push air our of his way
so that he could continue his parachute jump, and reach the ground
in time to be home for dinner.
