Pascal's Law

IMPORTANT

Pascal's Law: Overview

This topic covers concepts, such as, Atmospheric Pressure, Hydraulic Lift,Absolute Pressure and Units Used for Atmospheric Pressure etc.

Important Questions on Pascal's Law

MEDIUM
IMPORTANT

The pressure at the bottom of a tank of water is 3P where P is the atmospheric pressure. If the water is drawn out till the level of water is lowered by one-fifth, the pressure at the bottom of the tank will now be

MEDIUM
IMPORTANT

The area of cross-section of the wider tube shown in figure is 800 cm2. If a mass of 12 kg is placed on the massless piston, the difference in heights h in the level of water in the two tubes is

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HARD
IMPORTANT

For the system shown in the figure, the cylinder on the left at L has a mass of 600 kg and cross-sectional area of 800 cm2. The piston on the right, at S, has cross-sectional area 25 cm2 and negligible weight. If the apparatus is filled with oilρ=0.75gm cm-3. Find the force F required to hold the system in equilibrium

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EASY
IMPORTANT

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: When you squeeze one end of a tube to get toothpaste out from the other end, Pascal’s principle is observed.

Reason R: A change in the pressure applied to an enclosed incompressible fluid is transmitted undiminished to every portion of the fluid and to the walls of its container.

In the light of the above statements, choose the most appropriate answer from the options given below.

EASY
IMPORTANT

A manometer reads the pressure of a gas in an enclosure as shown in figure. The absolute and gauge pressure of the gas (in cm of mercury) in the enclosure is
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(Take atmospheric pressure = 76 cm of Hg)

MEDIUM
IMPORTANT

The height of mercury column in a simple barometer is h. As the tube is inclined with the vertical at an angle α, then length of mercury column along the length of the tube will become

MEDIUM
IMPORTANT

Calculate the barometer reading at a place where atmospheric pressure is 0.98 bar. Given that the density of mercury is 13.6×103 kg m-3.

EASY
IMPORTANT

A force of 500 N is executed on a hydraulic piston of cross sectional area of 100 cm2. The cross-sectional area of other piston which supports a truck of a tonne weight is [use g=9.8 m s-2]

EASY
IMPORTANT

In a hydraulic lift, compressed air exerts a force F on a small piston of radius 3 cm. Due to this pressure the second piston of radius 5 cm lifts a load of 1875 kg. The value of F is
(Acceleration due to gravity =10 m s-2)

EASY
IMPORTANT

The working of hydraulic lift is based on the principle of

MEDIUM
IMPORTANT

A car hoist is operated by a hydraulic as pictured. Determine compressive force F applied by hydraulic to keep the car-weight W in equilibrium at given position.

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EASY
IMPORTANT

A hydraulic lift is designed to lift heavy objects of maximum mass 2000 kg. The area of cross section of piston carrying the load is2.25×102m2 What is the maximum pressure the piston would have to bear?

HARD
IMPORTANT

Two vertical conducting cylinders A and B of different cross sections are connected by a thin tube as shown. An ideal gas is trapped in the cylinders by two airtight pistons of masses 1.0kg and 2.0kg respectively. Initially the pistons are at the same height 40cm above the base of the cylinders. If an additional mass of 10g were gently placed on the piston in the cylinder A, Which of the following statements correctly describe the new steady state ultimately reached.

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MEDIUM
IMPORTANT

A heavy load W is supported on a platform of area S by applying a force F on a small piston of area S10. The value of F for equilibrium is (x<<H)

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HARD
IMPORTANT

Some amount of water is trapped between two pistons, when can slide without friction in the vertical arms A and B of an S-shape tube. Area of horizontal crosssection of the arm B is η=5 times of the area SA=100 cm2 of the arm A. The piston in the arm B is supported on a spring of force constant k=1000 N m-1. In equilibrium, length of tube below the piston in arm B is t=20 cm. What maximum additional mass can be gently placed on the piston in the arm A so that piston in arm B will remain inside the tube ? Density of water is ρ=1000 kg m-3 and acceleration due to gravity is g=10 m s-2.

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HARD
IMPORTANT

A uniform rectangular narrow U-tube has equal arm lengths and base length, each equal to l. The vertical arms are filled with mercury up to l2 and then one end is sealed. By heating the enclosed gas all the mercury is expelled and collected at same level as the top most point of the tube. Assume ideal gas and ideal liquid conditions. If atmospheric pressure is P0, the density of mercury is ρ and cross-sectional area is S, then : [Neglect thermal expansion of glass and mercury, surface tension and viscosity effects and assume l2S]

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EASY
IMPORTANT

A dam of the water reservoir is built thinner at the bottom.

MEDIUM
IMPORTANT

Describe the factors determining the pressure exerted by liquids.

EASY
IMPORTANT

State Pascal's law.

EASY
IMPORTANT

Hydraulic press/lift is based on the principle of