The whole gravitational potential energy before taxiing is 2*M*g*R= the whole kinetic energy when taxiing to the bottom.

When the lock is released again, the maximum distance that the ball A can rise is h, and the gravitational potential energy of the ball A is M*g*H, which is the elastic potential energy when the spring is compressed.

Consider the energy in two states.

1. The sum of the energies of the ball A at the bottom of the semicircular groove is the kinetic energy of the ball A+the potential energy of the spring: m * g * r+m * g * h.

2. The gravitational potential energy M*g*h from the ball A to the highest point.

According to the law of conservation of energy

Yes, m * g * r+m * g * h = m * g * h

Get h = r+H.