Answer:
Change in potential energy, 
Explanation:
It is given that,
Mass of the ball, m = 0.5 kg
It is lifted to a height of, Initial height, h = 2 m
It bounces back to a height of 1.8 meters, final height, h' = 1.8 m
It can be assumed to find the change in potential energy in the entire process. Let
is the initial potential energy. It is given by :

Let
is the final potential energy. It is given by :

Let
is the change in potential energy. It is equal to :



So, the change in gravitational potential energy is 0.98 J. Hence, this is the required solution.