Question

Q-18 State Pascal's law for fluids with the help of a neat labelled diagram explain the principle and
working of hydraulic brakes.

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Answer 1

QUESTION:

State Pascal's law for fluids with the help of a neat labelled diagram explain the principle and

working of hydraulic brakes.

ANSWER:

Pascal's principle of hydrostatics, or Pascal's law, states that the pressure exerted anywhere in a confined incompressible liquid is equally transmitted throughout the fluid.

Explanation:

If a U-tube is filled with water and pistons are placed at each end, pressure exerted against the left piston will be transmitted throughout the liquid and against the bottom of the right piston. The pressure that the left piston exerts against the water will be exactly equal to the pressure the water exerts against the right piston. Suppose the tube on the right side is made wider and a piston of a larger area is used; for example, the piston on the right has 50 times the area of the piston on the left. If a 1 N load is placed on the left piston, an additional pressure due to the weight of the load is transmitted throughout the liquid and up against the larger piston. The difference between force and pressure is important: the additional pressure is exerted against the entire area of the larger piston. Since there is 50 times the area, 50 times as much force is exerted on the larger piston. Thus, the larger piston will support a 50 N load - fifty times the load on the smaller piston.

Forces can be multiplied using such a device. One newton input produces 50 newtons output. By further increasing the area of the larger piston, forces can be multiplied, in principle, by any amount. Pascal's principle underlies the operation of the hydraulic press. The hydraulic press does not violate energy conservation, because a decrease in distance moved compensates for the increase in force. When the small piston is moved downward 100 centimeters, the large piston will be raised only one-fiftieth of this, or 2 centimeters. The input force multiplied by the distance moved by the smaller piston is equal to the output force multiplied by the distance moved by the larger piston; this is one more example of a simple machine operating on the same principle as a mechanical lever.

A typical application of Pascal's principle for gases and liquids is the automobile lift seen in many service stations. Increased air pressure produced by an air compressor is transmitted through the air to the surface of oil in an underground reservoir. The oil, in turn, transmits the pressure to a piston, which lifts the automobile. The relatively low pressure that exerts the lifting force against the piston is about the same as the air pressure in automobile tires. Hydraulics is employed by modern devices ranging from very small to enormous. For example, there are hydraulic pistons in almost all construction machines where heavy loads are involved.

Answer 2

according to pascal's law

• Pascal's Law states that when pressure is applied to the fluid, the pressure change is transmitted uniformly in all directions and throughout the fluid.
• change in pressure applied to a fluid in a closed container is equally transmitted to every point in the fluid and also to the walls of the container.

• Mathematically, Pascal's Law can be expressed as:

P = F/A

where

the pressure exerted on a fluid is P

F = force applied to the fluid

the surface area over which the force is applied is A

• hydraulic brakes work on the principle of pascal's law.

• there are two pistons present in these breaks, one with a large area and the other with a small area.

• pressure applied at a small surface area produces pressure change that gets transmitted to the other piston with a large surface area

• the small surface produces more pressure for the same force because pressure and area are inversely related according to pascal's law

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