Q1: A short tube mouthpiece will not run full at its outlet if the head under which the orifice works, is

ANS:B - more than 12.2 m of the water

If the head under which the orifice works is more than 12.2 m of water, it suggests that the head or pressure head driving the flow through the orifice is greater than the critical value required for the orifice to run full. In fluid mechanics, when the head driving the flow through an orifice is higher than the critical value, the flow through the orifice will typically be unrestricted, and the orifice will run full at its outlet. This means that the flow will reach its maximum possible discharge given the geometry and conditions of the orifice. When the head exceeds the critical value, the additional energy available drives the flow through the orifice, ensuring that it operates at its maximum capacity. The excess head beyond the critical value contributes to the velocity and pressure of the fluid, allowing it to exit the orifice at a maximum discharge rate. In summary, if the head under which the orifice operates is more than 12.2 m of water, the orifice will typically run full at its outlet, ensuring that the flow reaches its maximum discharge capacity given the operating conditions.