ρ + ρgh = ρ , where ρ is density of water, h – height difference and and are the velocities in upper and lower cross sections correspondingly. We take into account that the pressure in both cross-sections is the same and equal to the atmospheric one.
From the continuity and assuming water incompressible:
= , where and are the corresponding cross-sections. As the lower diameter is twice as low as the upper one, we can conclude that
Inserting it back into Bernoulli equations produces: