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# Selina solutions for Concise Physics Class 9 ICSE chapter 4 - Pressure in Fluids and Atmospheric Pressure [Latest edition]

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#### Chapters ## Chapter 4: Pressure in Fluids and Atmospheric Pressure

Exercise - 4(A)Exercise - 4(B)

#### Selina solutions for Concise Physics Class 9 ICSE Chapter 4 Pressure in Fluids and Atmospheric Pressure Exercise Exercise - 4(A) [Pages 92 - 93]

Exercise - 4(A) | Q 1 | Page 92

Define the term thrust. State its S.I. unit.

Exercise - 4(A) | Q 2 | Page 92

What is meant by pressure? State its S.I. unit.

Exercise - 4(A) | Q 3.1 | Page 92

What physical quantity is measured in bar?

Exercise - 4(A) | Q 3.2 | Page 92

How is the unit bar related to the S.I. unit pascal?

Exercise - 4(A) | Q 4 | Page 92

Define one pascal (Pa), the S.I. unit of pressure.

Exercise - 4(A) | Q 5 | Page 92

tate whether thrust is a scalar or vector?

Exercise - 4(A) | Q 6 | Page 92

State whether pressure is a scalar or vector?

Exercise - 4(A) | Q 7 | Page 92

Differentiate between thrust and pressure.

Exercise - 4(A) | Q 8 | Page 92

How does the pressure exerted by thrust depend on the area of surface on which it acts? Explain with a suitable example.

Exercise - 4(A) | Q 9 | Page 92

Why is the tip of an allpin made sharp?

Exercise - 4(A) | Q 10.1 | Page 92

Explain the following statement:
It is easier to cut with a sharp knife than with a blunt one.

Exercise - 4(A) | Q 10.2 | Page 92

Explain the following statement:
Sleepers are laid below the rails.

Exercise - 4(A) | Q 11 | Page 92

What is a fluid?

Exercise - 4(A) | Q 12 | Page 92

What do you mean by the term fluid pressure?

Exercise - 4(A) | Q 13 | Page 92

How does the pressure exerted by a solid and fluid differ?

Exercise - 4(A) | Q 14 | Page 92

Describe a simple experiment to demonstrate that a liquid enclosed in a vessel exerts pressure in all directions.

Exercise - 4(A) | Q 15 | Page 92

State three factors on which the pressure at a point in a liquid depends.

Exercise - 4(A) | Q 16 | Page 92

Write an expression for the pressure at a point inside a liquid. Explain the meaning of the symbols used.

Exercise - 4(A) | Q 17 | Page 92

Deduce an expression for the pressure at depth inside a liquid.

Exercise - 4(A) | Q 18 | Page 92

How does the pressure at a certain depth in sea water differ from that at the same depth in river water? Explain your answer.

Exercise - 4(A) | Q 19 | Page 92

Pressure at the free surface of a water lake is P1, while at a point at depth h below its free surface is P2. (a) How are P1 and P2 related? (b)Which is more P1 or P2?

Exercise - 4(A) | Q 20 | Page 92

Explain why a gas bubble released at the bottom of a lake grows in size as it rises to the surface of the lake.

Exercise - 4(A) | Q 21 | Page 92

A dam has broader walls at the bottom than at the top. Explain.

Exercise - 4(A) | Q 22 | Page 92

Why do sea divers need special protective suit?

Exercise - 4(A) | Q 23 | Page 92

State the laws of liquid pressure.

Exercise - 4(A) | Q 24 | Page 92

A tall vertical cylinder filled with water is kept on a horizontal table top . Two small holes A and B are amde on the wall of the cylinder , A near the middle and B just Below the free surface of water . state and explain your observation.

Exercise - 4(A) | Q 25.1 | Page 92

How does the liquid pressure on a diver change if:

the diver moves to the greater depth

Exercise - 4(A) | Q 25.2 | Page 92

How does the liquid pressure on a diver change if :

The diver moves horizontally?

Exercise - 4(A) | Q 26 | Page 92

State Pascal's law of transmission of pressure.

Exercise - 4(A) | Q 27 | Page 93

Name two applications of Pascal's law.

Exercise - 4(A) | Q 28 | Page 93

Explain the principle of a hydraulic machine. Name two devices which work on this principle.

Exercise - 4(A) | Q 29 | Page 93

Name and state the principle on which a hydraulic press works. Write one use of hydraulic press.

Exercise - 4(A) | Q 30 | Page 93

The diagram below in Fig. 4.12 shows a device which makes the use of the principle of transmission of pressure. (i) Name the parts labelled by the letters X and Y.

(ii) Describe what happens to the valves A and B and to the quantity of water in the two cylinders when the lever arm is moved down

(iii) Give reasons for what happens to the valves

A and B

(iv) What happens when the release valve is opened?

(v) What happens to the valve B in cylinder P when the lever arm is moved up?

(vii) State one use of the above device.

Exercise - 4(A) | Q 31 | Page 93

Draw a simple diagram of a hydraulic jack and explain its working.

Exercise - 4(A) | Q 32 | Page 93

Explain the working of a hydraulic brake with a simple labelled diagram.

Exercise - 4(A) | Q 33.1 | Page 93

Complete the following sentence :

Pressure at a depth h in a liquid of density p is ......................

Exercise - 4(A) | Q 33.2 | Page 93

Complete the following sentence :

Pressure is .................... in all directions about a point in a liquid.

Exercise - 4(A) | Q 33.3 | Page 93

Complete the following sentence :

Pressure at all points at the same depth is ....................

Exercise - 4(A) | Q 33.4 | Page 93

Complete the following sentence :

Pressure at a point inside the liquid is ...................... To its depth.

Exercise - 4(A) | Q 33.5 | Page 93

Complete the following sentence :

Pressure of a liquid at a given depth is .................. To the density of the liquid.

#### Selina solutions for Concise Physics Class 9 ICSE Chapter 4 Pressure in Fluids and Atmospheric Pressure Exercise Exercise - 4(A) [Page 93]

Exercise - 4(A) | Q 1 | Page 93

The S.I. unit of pressure is :

• N cm-2

• Pa

• N

• N m2

Exercise - 4(A) | Q 2 | Page 93

The pressure inside a liquid of density p at a depth h is :

• h ρ g

• h/(ρg)

• (hρ)/g

• hρ

Exercise - 4(A) | Q 3 | Page 93

The pressure P1 at a certain depth in river water and P2 at the same depth in sea water are related as :

• P1 > P2

• P1= P2

• P1 < P2

• P1 -  P= atmospheric pressure

Exercise - 4(A) | Q 4 | Page 93

The pressure P1 at the top of a dam and Pat a depth h form the top inside water (density p) are related as :

• P1 > P2

• P1 = P2

• P1 -  P2 = h ρ g

• P2 -  P1 = h ρ g

#### Selina solutions for Concise Physics Class 9 ICSE Chapter 4 Pressure in Fluids and Atmospheric Pressure Exercise Exercise - 4(A) [Pages 93 - 94]

Exercise - 4(A) | Q 1 | Page 93

A hammer exerts a force of 1.5 N on each of the two nails A and B. The area of cross section of tip of nail A is 2 mm2 while that of nail B is 6 mm2. Calculate pressure on each nail in pascal.

Exercise - 4(A) | Q 2 | Page 93

A block of iron of mass 7.5 kg and of dimensions 12 cm × 8 cm × 10 cm is kept on a table top on its base of side 12 cm × 8 cm.

Calculate :

1. Thrust and
2. Pressure exerted on the table top

Take 1 kgf = 10 N.

Exercise - 4(A) | Q 3 | Page 93

A vessel contains water up to a height of 1.5 m. Taking the density of water 103 kg m-3, acceleration due to gravity 9.8 m s-2 and area of base of vessel 100 cm2, calculate: (a) the pressure and (b) the thrust at the base of vessel.

Exercise - 4(A) | Q 4 | Page 93

The area of base of a cylindrical vessel is 300 cm2. Water (density= 1000 kg m-3) is poured into it up to a depth of 6 cm. Calculate : (a) the pressure and (b) the thrust of water on the base. (g = 10m s-2.

Exercise - 4(A) | Q 5 | Page 93

(a) Calculate the height of a water column which will exert on its base the same pressure as the 70 cm column of mercury. Density of mercury is 13.6 g cm-3.

(b) Will the height of the water column in part (a) change if the cross section of the water column is made wider?

Exercise - 4(A) | Q 6 | Page 94

The pressure of water on the ground floor is 40,000 Pa and on the first floor is 10,000 Pa. Find the height of the first floor. (Take : density of water = 1000 kg m-3, g = 10 m s-2)

Exercise - 4(A) | Q 7 | Page 94

A simple U tube contains mercury to the same level in both of its arms. If water is poured to a height of 13.6 cm in one arm, how much will be the rise in mercury level in the other arm?

Given : density of mercury = 13.6 x 103 kg m-3 and density of water = 103 kg m-3.

Exercise - 4(A) | Q 8 | Page 94

In a hydraulic machine, a force of 2 N is applied on the piston of area of cross section 10 cm2. What force is obtained on its piston of area of cross section 100 cm2 ?

Exercise - 4(A) | Q 9 | Page 94

What should be the ratio of area of cross section of the master cylinder and wheel cylinder of a hydraulic brake so that a force of 15 N can be obtained at each of its brake shoe by exerting a force of 0.5 N on the pedal ?

Exercise - 4(A) | Q 10 | Page 94

The areas of pistons in a hydraulic machine are 5 cm2 and 625 cm2. What force on the smaller piston will support a load of 1250 N on the larger piston? State any assumption which you make in your calculation.

Exercise - 4(A) | Q 11 | Page 94

(i) The diameter of neck and bottom of a bottle are 2 cm and 10 cm, respectively. The bottle is completely filled with oil. If the cork in the neck is pressed in with a force of 1.2 kgf, what force is exerted on the bottom of the bottle?

(ii) Name the law/principle you have used to find the force in part (a).

Exercise - 4(A) | Q 12 | Page 94

A force of 50 kgf is applied to the smaller piston of a hydraulic machine. Neglecting friction, find the force exerted on the large piston, if the diameters of the pistons are 5 cm and 25 cm respectively.

Exercise - 4(A) | Q 13 | Page 94

Two cylindrical vessels fitted with pistons A and B of area of cross section 8 cm2 and 320 cm2 respectively, are joined at their bottom by a tube and they are completely filled with water. When a mass of 4 kg is placed on piston A, Find : (i) the pressure on piston A, (ii) the pressure on piston B, and (iii) the thrust on piston B.

Exercise - 4(A) | Q 14 | Page 94

What force is applied on a piston of area of cross section 2 cm2 to obtain a force 150 N on the piston of area of cross section 12 cm2 in a hydraulic machine?

#### Selina solutions for Concise Physics Class 9 ICSE Chapter 4 Pressure in Fluids and Atmospheric Pressure Exercise Exercise - 4(B), Exercise - 4(A) [Pages 101 - 102]

Exercise - 4(B) | Q 1 | Page 101

What do you understand by atmospheric pressure?

Exercise - 4(B) | Q 2 | Page 101

Write the numerical value of the atmospheric pressure on the surface of earth in pascal.

Exercise - 4(B) | Q 3 | Page 101

What physical quantity is measured in torr? How is it related to the S.I. unit of the quantity?

Exercise - 4(B) | Q 4 | Page 101

Name the physical quantity which is expressed in the unit 'atm'. State its value in pascal.

Exercise - 4(A) | Q 5 | Page 101

We do not feel uneasy even under enormous pressure of the atmosphere above as well as around us. Give a reason.

Exercise - 4(B) | Q 6 | Page 101

Describe an experiment to demonstrate that air exerts pressure.

Exercise - 4(B) | Q 7.1 | Page 101

Explain the following :

A balloon collapses when air is removed from it.

Exercise - 4(B) | Q 7.2 | Page 101

Explain the following :

Water does not run out of a dropper unless its rubber bulb is pressed .

Exercise - 4(B) | Q 7.3 | Page 101

Explain the following :

Two holes are made in a completely filled sealed tin can to take out oil from it .

Exercise - 4(B) | Q 8 | Page 101

Why does the liquid rise in a syringe when its piston is pulled up?

Exercise - 4(B) | Q 9 | Page 101

How is water drawn up from a well by a water pump?

Exercise - 4(B) | Q 10 | Page 101

A partially inflated balloon is placed inside a bell jar connected to a vacuum pump. On creating vacuum inside the bell jar, balloon gets more inflated. How does the pressure change : increase, decrease or remains same , inside the (a) bell jar ,(b) balloon ?

Exercise - 4(B) | Q 11 | Page 101

What is the purpose of a barometer?

Exercise - 4(B) | Q 12 | Page 101

What is a barometer ? How is a simple barometer constructed ?

Exercise - 4(B) | Q 13 | Page 101

Explain how is the height of mercury column in tube of a simple barometer, a measure of the atmospheric pressure.

Exercise - 4(B) | Q 14 | Page 101

Illustrate with the help of a labelled diagram of a simple barometer that the atmospheric pressure at a place is 76 cm of Hg.

Exercise - 4(B) | Q 15 | Page 101

Why is the barometric height used as unit to express the atmospheric pressure?

Exercise - 4(B) | Q 16 | Page 101

What is meant by the statement 'the atmospheric pressure at a place is 76 cm of Hg'? State its value in Pa.

Exercise - 4(B) | Q 17 | Page 101

How will you show that there is vacuum above the surface of mercury in a barometer? What name is given to this vacuum?

Exercise - 4(B) | Q 18.1 | Page 102

How is the barometric height of a simple barometer affected if  Its tube is pushed down into the trough of mercury?

Exercise - 4(B) | Q 18.2 | Page 102

How is the barometric height of a simple barometer affected if  Its tube is slightly tilted from vertical?

Exercise - 4(B) | Q 18.3 | Page 102

How is the barometric height of a simple barometer affected if A drop of liquid is inserted inside the tube?

Exercise - 4(B) | Q 19 | Page 102

State two uses of a barometer.

Exercise - 4(B) | Q 20 | Page 102

Give two reasons for use of mercury as a barometric liquid.

Exercise - 4(B) | Q 21 | Page 102

Give two reasons why water is not a suitable barometric liquid.

Exercise - 4(B) | Q 22 | Page 102

Mention two demerits of a simple barometer and state how they are removed in a Fortin barometer .

Exercise - 4(B) | Q 23 | Page 102

Draw a simple labelled diagram of a Fortin barometer and state how it is used to measure the atmospheric pressure.

Exercise - 4(B) | Q 24 | Page 102

What is an aneroid barometer? Draw a neat and labelled diagram to explain its construction and working.

Exercise - 4(B) | Q 25 | Page 102

State two advantages of an aneroid barometer over a simple barometer.

Exercise - 4(B) | Q 26 | Page 102

How is the reading of a barometer affected when it is taken to (i) a mine, and (ii) a hill?

Exercise - 4(B) | Q 27 | Page 102

How does the atmospheric pressure change with altitude? Draw an approximate graph to show this variation.

Exercise - 4(B) | Q 28 | Page 102

State two factors which affect the atmospheric pressure as we go up.

Exercise - 4(B) | Q 29 | Page 102

Why does a fountain pen leak at high altitude?

Exercise - 4(B) | Q 30 | Page 102

Why does nose start bleeding on high mountains?

Exercise - 4(B) | Q 31 | Page 102

What is an altimeter? State its principle. How is its scale calibrated?

Exercise - 4(B) | Q 32.1 | Page 102

What do the following indicate in a barometer regarding weather : gradual fall in the mercury level

Exercise - 4(B) | Q 32.2 | Page 102

What do the following indicate in a barometer regarding weather : sudden fall in the mercury level

Exercise - 4(B) | Q 32.3 | Page 102

What do the following indicate in a barometer regarding weather : Gradual rise in the mercury level?

#### Selina solutions for Concise Physics Class 9 ICSE Chapter 4 Pressure in Fluids and Atmospheric Pressure Exercise Exercise - 4(B) [Page 102]

Exercise - 4(B) | Q 1 | Page 102

The unit torr is related to the barometric height as :

•  1 torr = l cm of Hg

•  1 torr = 0.76 m of Hg

• 1 torr = 1 mm of Hg

• 1 torr = 1m of Hg

Exercise - 4(B) | Q 2 | Page 102

The normal atmospheric pressure is :

• 76 m of Hg

• 76 cm of Hg

• 76 Pa

• 76 N m-2

Exercise - 4(B) | Q 3 | Page 102

The atmospheric pressure at earth's surface is P1 and inside mine is P2. They are related as :

• l =P2

• l > P2

•  P l <  P2

• P2 = 0

#### Selina solutions for Concise Physics Class 9 ICSE Chapter 4 Pressure in Fluids and Atmospheric Pressure Exercise Exercise - 4(B) [Page 102]

Exercise - 4(B) | Q 1 | Page 102

Convert 1 mm of Hg into pascal. Take density of Hg = 13.6 x 103 kg m-3 and g = 9.8 m s-2 .

Exercise - 4(B) | Q 2 | Page 102

At a given place, a mercury barometer records a pressure of 0.70 m of Hg. What would be the height of water column if mercury in barometer is replaced by water? Take density of mercury to be  = 13.6 × 103 kg m-3.

Exercise - 4(B) | Q 3 | Page 102

At sea level, the atmospheric pressure is 76 cm of Hg. If air pressure falls by 10 mm of Hg per 120m of ascent, what is the height of a hill where the barometer reads 70 cm Hg. State the assumption made by you.

Exercise - 4(B) | Q 4 | Page 102

At sea level, the atmospheric pressure is 1.04 x 105 Pa. Assuming g = 10 m s-2 and density of air to be uniform and equal to 1.3 kg m-3, find the height of the atmosphere.

Exercise - 4(B) | Q 5 | Page 102

Assuming the density of air to be 1.295 kg m-3, find the fall in barometric height in mm of Hg at a height of 107 m above the sea level. Take density of mercury = 13.6 × 103 kg m-3.

## Chapter 4: Pressure in Fluids and Atmospheric Pressure

Exercise - 4(A)Exercise - 4(B) ## Selina solutions for Concise Physics Class 9 ICSE chapter 4 - Pressure in Fluids and Atmospheric Pressure

Selina solutions for Concise Physics Class 9 ICSE chapter 4 (Pressure in Fluids and Atmospheric Pressure) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CISCE Concise Physics Class 9 ICSE solutions in a manner that help students grasp basic concepts better and faster.

Further, we at Shaalaa.com provide such solutions so that students can prepare for written exams. Selina textbook solutions can be a core help for self-study and acts as a perfect self-help guidance for students.

Concepts covered in Concise Physics Class 9 ICSE chapter 4 Pressure in Fluids and Atmospheric Pressure are Change of Pressure with Depth, Transmission of Pressure in Liquids, Pascal's Law, Atmospheric Pressure, Buoyancy, Archimedes' Principle, Floatation - Principle of Floatation, Relation Between the Density of a Floating Body, Determination of Relative Density of a Solid, Change of Pressure with Depth, Transmission of Pressure in Liquids, Pascal's Law, Atmospheric Pressure, Buoyancy, Archimedes' Principle, Floatation - Principle of Floatation, Relation Between the Density of a Floating Body, Determination of Relative Density of a Solid, Introduction of Fluid.

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