NEIEP Mechanics Practice Exam

What is the scientific principle that governs the operation of a hydraulic elevator?

1. Bernoulli's Principle

2. Pascal's Law

3. Archimedes' Principle

4. Newton's Third Law

The correct answer is: Pascal's Law

The operation of a hydraulic elevator is governed by Pascal's Law, which states that when pressure is applied to a confined fluid, this pressure is transmitted undiminished throughout the fluid in all directions. This principle is crucial for the functioning of hydraulic systems, including elevators, where the application of force to a small piston creates a pressure increase that is transmitted to a larger piston, resulting in a greater lifting force. In the hydraulic elevator, a pump moves fluid (usually oil) into a cylinder that contains a piston. As the fluid is forced into the cylinder, the piston moves upward, which lifts the elevator. The design utilizes the incompressibility of liquids and Pascal's Law ensures that the force applied to one area translates to a proportional force at another area, allowing for efficient lifting of heavy loads with comparatively little effort. This ability to multiply force is what makes hydraulic systems very effective in applications like elevators. Other principles listed, such as Bernoulli's Principle, primarily deal with fluid dynamics and the behavior of fluids in motion, Archimedes' Principle relates to buoyancy in fluids, and Newton's Third Law addresses action and reaction forces, but they do not specifically explain the mechanics of hydraulic systems as directly as Pascal's Law does.