Answer:
15.5 J
Explanation:
The total (mechanical) energy of an object is given by
E = K + U
where
K is the kinetic energy
U is the gravitational potential energy
The ball in the problem, when it left the hand, has:
K = 7.2 J (kinetic energy)
U = 8.3 J (potential energy)
So, its total mechanical energy is
E = 7.2 + 8.3 = 15.5 J