Final answer:
A hydraulic jack leverages the physics of fluid mechanics to lift heavy loads by applying a small force on one side to exert a larger force on the other.
Step-by-step explanation:
The student's question refers to the use of a hydraulic jack to lift vehicles, which is a topic related to Physics, specifically within the concept of fluid mechanics.
A hydraulic jack operates by the physics principle that when a small force is applied to a piston in a narrow part of a U-shaped tube filled with incompressible fluid, it can exert a much greater force on a larger piston at the other end. This is because the pressure applied to the fluid is distributed evenly throughout the system.
Therefore, when an auto mechanic uses a hydraulic jack, they are taking advantage of this principle to lift heavy loads such as a car. The recommendation to lift a vehicle at the axle is related to ensuring the stability and safety of the lift operation.