A type of pump that uses the velocity of steam against the mass of water is known as what?

The type of pump that utilizes the velocity of steam to impart energy to a mass of water is the injector. This device operates by creating a high-speed jet of steam, which entrains and accelerates water, effectively using the kinetic energy of the steam to move water. Injectors are commonly employed in steam systems, particularly in applications where it's necessary to add water to a steam boiler.

They work based on Bernoulli's principle, where the steam's velocity decreases as it expands, creating a vacuum that pulls in and mixes with the water. As a result, the combination of steam and water is discharged at a higher velocity.

Other types of pumps, such as centrifugal and reciprocating pumps, operate based on different principles, such as the movement of impellers or pistons, rather than using a steam jet to create flow. Gravity pumps rely on gravitational force and are not applicable in this context. Therefore, the injector is the correct choice, as it specifically employs steam velocity to achieve the desired action of moving water.