Pascals Law

  • State Pascal’s law.

  • Apply Pascal’s Principle to describe pressure behavior in static fluids

The normal stresses at any point in a fluid element at rest are directed towards the point from all directions and they are of the equal magnitude.

Units and scales of Pressure Measurement:

Pascal \((N/m^2)\) is the unit of pressure. Pressure is usually expressed with reference to either absolute zero pressure (a complete vacuum) or local atmospheric pressure.

  • Absolute pressure: It is the difference between the value of the pressure and the absolute zero pressure.

  • Gauge pressure: It is the difference between the value of the pressure and the local atmospheric pressure.

At sea-level, the international standard atmosphere has been chosen as = 101.32 \(kN/m^2\)

Solved Examples

Solved Example:

61-1-01

1 GPa is equivalent of:

Correct Answer: C

Solved Example:

61-1-02

Liquids transmit pressure equally in all the directions. This is according to:

Solution:
Boyle's law states that the pressure (p) of a given quantity of gas varies inversely with its volume (v) at constant temperature; i.e., in equation form, pv = k, a constant.
Archimedes' principle states: An object immersed in a fluid experiences a buoyant force that is equal in magnitude to the force of gravity on the displaced fluid.
There is no such thing called Newton's formula. We have Newton's laws and Newton's equation of motion.
Pascal's law says that pressure applied to an enclosed fluid will be transmitted without a change in magnitude to every point of the fluid and to the walls of the container. The pressure at any point in the fluid is equal in all directions.

Correct Answer: C

Solved Example:

61-1-03

A hydraulic press has a ram of 15 cm diameter and plunger of 1.5 cm. It is required to lift a weight of 1000 kg. The force required on the plunger is equal to: (NPCIL Stipendiary Trainee ME 2018)

Correct Answer: A

Solved Example:

61-1-04

The hydraulic lift is based on which of the following? (SSC Scientific Assistant Physics Nov 2017- Shift II)

Correct Answer: B

Solved Example:

61-1-05

A hydraulic press has a ram of 20 cm diameter and a plunger of 3 cm diameter. It is used for lifting a weight of 30 kN. Find the force required at the plunger. (SSC JE ME Oct 2020 Evening)

Correct Answer: C

Solved Example:

61-1-06

As per Pascal's law: (SSC JE CE Oct 2020 Evening)

Correct Answer: B

Solved Example:

61-1-07

_____ gives an idea about the pressure in a static fluid. (SSC JE ME Oct 2020 Evening)

Correct Answer: C

Solved Example:

61-1-08

Which of the following statements is INCORRECT in the context of static fluid pressure? (SSC JE ME Mar 2021 Evening)

Correct Answer: A

Solved Example:

61-1-09

A hydraulic press has a ram of 300 mm diameter and a plunger of 45 mm diameter. When the force applied at the plunger is 50 N, the weight lifted by the hydraulic press will be nearly: (ESE Civil 2020)

Correct Answer: B