Question

With reference to point B 
 

Hint:

When the sluice gate at point B opens, the water's potential energy (from being stored at higher levels) turns into kinetic energy as it flows down through the penstock to the turbine. This process is key in generating hydroelectric power, as the moving water drives the turbine to produce electricity!

Answer 1

When the sluice gate at point B is opened, the stored water above the gate (water at levels A and B in the reservoir) flows through the gate and its potential energy is converted into kinetic energy as it moves down the penstock towards the turbine.