What source of energy allows liquid to enter a pump with suction lift?

The correct answer, atmospheric pressure, is critical in allowing liquid to enter a pump with suction lift because it is the force that drives the fluid into the pump. When a pump is placed above the liquid source, it creates a vacuum inside the pump housing as it operates, lowering the pressure within it. The difference in pressure between the atmospheric pressure outside the pump and the reduced pressure inside the pump facilitates the movement of the liquid from the source into the pump.

As atmospheric pressure exerts force on the surface of the liquid in the reservoir, it pushes the liquid up into the pump. This principle is based on the idea that fluids naturally flow from areas of higher pressure to areas of lower pressure, thereby allowing the liquid to be lifted into the pump despite the suction lift scenario.

In this context, sources like weight of the liquid may contribute to the overall dynamics but are not primarily responsible for drawing the liquid into the pump. Similarly, velocity energy considers the movement of the fluid but doesn't directly affect suction lift operational principles. The sucking action of the impeller is pertinent to pump operation but is dependent on the external atmospheric pressure to initiate flow when dealing with suction lift.