Hydrostatics principle in devices Which unit operates primarily on Pascal's law (pressure applied to a confined fluid is transmitted undiminished in all directions)?

Mechanical Engineering Hydraulic Machines Difficulty: Easy
Choose an option
  • A
    Air lift pump
  • B
    Jet pump
  • C
    Hydraulic coupling
  • D
    Hydraulic press
  • E
    Venturimeter

Answer

Correct Answer: Hydraulic press

Explanation

Introduction / Context:Pascal’s law underpins many hydraulic machines where force multiplication is achieved through static pressure transmission in incompressible fluids. Recognizing which devices rely on hydrostatics versus hydrodynamics is essential for correct selection and analysis.

Given Data / Assumptions:

  • Incompressible fluid and sealed system for Pascal’s principle.
  • Quasi-static operation where dynamic effects are negligible.

Concept / Approach:Pascal’s law: a pressure increment applied to a confined fluid is transmitted equally to every point and to the walls of the container. A hydraulic press uses two pistons of different areas connected by fluid; equal pressure gives F_out / F_in = A_out / A_in, yielding mechanical advantage.

Step-by-Step Solution:Apply an input force on the small piston creating pressure p = F_in / A_in.The same pressure acts on the large piston: F_out = p * A_out.Therefore F_out / F_in = A_out / A_in, demonstrating force amplification.

Verification / Alternative check:Energy balance (ignoring losses): F_in * s_in ≈ F_out * s_out, consistent with the area ratio trade-off.

Why Other Options Are Wrong:Air lift pump and jet pump exploit fluid momentum and entrainment (hydrodynamics). Hydraulic coupling transmits torque via circulating oil and relative motion, not static pressure multiplication. A venturimeter measures flow using Bernoulli’s principle, not Pascal’s law.

Common Pitfalls:Confusing pressure transmission (static) with momentum transfer (dynamic). Assuming any “hydraulic” device uses Pascal’s law, which is not always true.

Final Answer:Hydraulic press

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