class 9 holiday homework (all subjects)

Delhi Public School Ghaziabad Vasundhara SUBJECT : ENGLISH

CLASS: IX

Lesson: The Seven Ages Objectives:

• The students will get a hang of Shakespeare’s poetic genius. • They will be able to distinguish the various stages in a man’s life and characteristics associated with them. • They will understand the transitory nature of human life and various stages. • The poem will make children more sensitive and tolerant towards the people of different age groups.

Getting started Q.1 Broadly speaking, there are three stages in a man’s life. Now tell me, which stage of life do you belong to?

What are the characteristic features associated with it? Q.2 List the various stages of man’s life you know, if you don’t know- think, guess and let your mind run wild

and write whatever strikes you.

Brief introduction: The poem ‘The Seven Ages’ has been taken from Shakespeare’s famous play ‘As You Like It’. In the poem, the poet compares life to a drama, in which a person plays many parts as he / she progresses through life. Man in one life plays these seven parts progressively: Infant – School boy – Lover – Soldier – Justice – Old man – Extreme old age.

Q.3 Now read lines 1-18 (All the world ………… modern instances.) and then read the following interpretation of difficult words and phrases for better understanding.

And all the men and women merely players: all the men and women are like actors on the stage of the

world. They have their exits and entrances: People come (take birth or take entry) on this stage, play different

roles in their life and then go away (move out through the exit). And then the lover, sighing like a furnace: the lover sighs deeply like a furnace when his love is not

responded by his beloved. Then the soldier…… reputation: A soldier is very ambitious and is ready to sacrifice his life for short

lived reputation. TEST YOUR UNDERSTANDING Q.4 Answer the following questions to test, refine and extend your understanding. (i) Why does the poet compare the world to a stage? (ii) Which stage of man’s life do you like the most? Give reasons to support your answer. (iii) Identify the various stages of man’s life and note down the characteristic features of each stage as shown

below: Stage Characteristic features

Infancy School boy Lover Soldier Justice

Crying

Let’s summarize:

The poet has compared the world to a stage. In the drama of life man first plays the role of an infant then of a school boy who is unwilling to go to school. The third stage is of a lover who sings ballads in praise of his mistress. Then man enacts the role of a soldier who is like a leopard and is ready to sacrifice his life for short lived reputation. In the fourth stage of life, wisdom dawns on man and he becomes wise like a judge.

Q.5 Now read lines 19-28 (The sixth ………… sans everything) and then read the following interpretation of

difficult words and phrases for better understanding. With spectacles on nose and pouch on side: when the man becomes lean, thin and weak, his spectacles

fall on his nose and the soft fold of the loose skin hangs from his face.

His youthful …… shank: the trousers which he used to wear in his youth get loose on his body. TEST YOUR UNDERSTANDING

Q.6 Answer the following questions to test, refine and extend your understanding. (i) Mention at least two examples of physical degeneration that takes place in the sixth stage of life (ii) Why is the extreme old age compared to second childishness? (iii) What happens to the booming voice of a man in old age?

Let’s summarize: In the sixth stage, man becomes old, lean and thin the trousers that he used to wear in his youth get loose on his body his impressive and manly voice becomes weak like that of a child in the last stage, man becomes helpless as a baby he loses his memory and other faculties he loses his teeth, his eyes, his taste and all the charms of life

he becomes completely oblivious

SELF- ASSESSMENT

Q.7 Answer the following questions briefly in about 35-40 words each. (i) Explain the line ’They have their exits and entrances’. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ (ii) Why does the poet compare the schoolboy to a snail? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

(iii) Briefly describe the look and the behaviour of the justice. ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ (iv) Why is the last stage of a man’s life described as ‘second childishness’? ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Helpline Number : 9818742027

Delhi Public School Ghaziabad Vasundhara SUBJECT:CHEMISTRY

CLASS: IX CHAPTER 3:ATOMS AND MOLECULES

Goal: To appreciate the diversity in the laws of chemical combinations and used it in daily life. Objective: You will be able to: i. Define matter and its composition. ii. Identify the law of combination of mass. iii. Compare the laws of combination. iv. Illustrate the Dalton’s atomic theory. v. Solve the numerical based on laws of chemical combination.

LAWS OF CHEMICAL COMBINATION

Antoine L. Lavoisier laid the foundation of chemical sciences by establishing two important laws of chemical combination. These laws were established after much experimentations by Lavoisier . Antoine Lavoisier (1743-1794) is often called the father of modern chemistry. Lavoisier lived during the French Revolution, and he brought about a scientific revolution in chemistry. He is possibly the greatest scientist France ever produced, but his scientific eminence was not enough to save him from the guillotine in 1794. The son of a wealthy Parisian lawyer, Lavoisier completed a law degree to please his parents, but his real interest was in science. In 1768 he was elected to the prestigious French Academy of Sciences in which he was a rising star, becoming director in 1785.

When substances react, they do so by following certain laws. These laws are called the laws of chemical combination.

Law of conservation of mass

Stated by French chemist A. Lavoisier "During any physical or chemical change, the total mass of the products remains equal to the total mass of the reactants". Law of conservation is also known as 'Law of indestructibility of matter'.

Example

10 grams of CaCO3 on heating gave 4.4g of CO2 and 5.6 of CaO. Show that these observations are in agreement with the law of conservation.

Solution:

Mass of the reactants = 10g

Mass of the products = 4.6 + 5.6g = 10g

Since the mass of the reactants is equal to the mass of the products, the observations are in agreement with the law of conservation of mass.

Law of constant proportion

Stated by French chemist Joseph Proust “A chemical compound always contains same elements combined together in the same proportion by mass”.

For example, pure water obtained from different sources such as river, well, springs, sea, etc., always contains hydrogen and oxygen together in the ratio of 1: 8 by mass. Similarly, CO2 can be obtained by different methods such as,

• burning of carbon

• heating of lime stone

• by action of dilute HCl on marble pieces

The different samples of CO2 contain carbon and oxygen in the ratio of 3: 8.

Example

1.375g of cupric oxide was reduced by heating in a current of hydrogen and the weight of copper that remained was 1.098g. In another experiment 1.179g of copper was dissolved in nitric acid and resulting copper nitrate converted into cupric oxide by ignition. The weight of cupric oxide formed was 1.476g. Show that these results illustrate the law of constant proportion.

Solution

First experiment

Copper oxide = 1.375g

Copper left = 1.098g

Oxygen present = 1.375 - 1.098 = 0.277g

Second experiment

Copper taken = 1.179g

Copper oxide formed = 1.476g

Oxygen present = 1.476 - 1.179 = 0.297g

Percentage of oxygen is same in both the above cases so the law of constant composition is illustrated.

Law of multiple proportions

Stated by John Dalton (1803)

"When two elements combine with each other to form two or more than two compounds, the masses of one the element which combine with the fixed mass of the other, bears a simple whole number ratio".

Examples

Carbon monoxide (CO): 12 parts by mass of carbon combines with 16 parts by mass of oxygen.

Carbon dioxide (CO2): 12 parts by mass of carbon combines with 32 parts by mass of oxygen.

Ratio of the masses of oxygen that combines with a fixed mass of carbon (12 parts) 16: 32 or 1: 2

For example, hydrogen and oxygen are known to form 2 compounds. The hydrogen content in one is 5.93% while in the other it is 11.2%. Show that this data illustrates the law of multiple proportions.

Solution

In the first compound hydrogen = 5.93%

Oxygen = (100 -5.93) = 94.07%

In the second compound

Hydrogen = 11.2%

Oxygen = (100 -11.2) = 88.88%

In the first compound the number of parts of oxygen that combine with one part by mass of hydrogen

In the second compound the number of parts by mass of oxygen that combine with one part by mass of hydrogen

Ratio of the masses of oxygen that combine with fixed mass of hydrogen 15.86: 7.9 or 2:1

The ratio illustrates the law of multiple proportion.

Dalton’s Atomic Theory

Dalton’s atomic theory – John Dalton proposed the basic theory about the nature of matter. The postulates of his theory are as follows: (i) All matter, whether an element, a compound, or a mixture is composed of very tiny particles called atoms. (ii) Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction. (iii) Atoms of a given element are identical in mass and chemical properties. (iv) Atoms of different elements have different masses and chemical properties. (v) Atoms combine in the ratio of small whole numbers to form compounds. (vi) The relative number and kinds of atoms are constant in a given compound.

• Dalton’s atomic theory was based on the laws of chemical combination. The postulate of Dalton’s atomic theory that “atoms can neither be created nor destroyed” was the result of law of conservation of mass.

• The postulate that “ the elements consist of atoms having fixed mass”, and that “the number and kind of atoms in a given compound is fixed” came from the law of constant proportions.

His theory also provided an explanation for the laws of chemical combination. • According to his theory atoms can neither be created nor destroyed. Since this is true, therefore, the

number of various types of atoms in the products of a chemical reaction is the same as the number of all those atoms in the reactants. The same number of various atoms in products and reactants will have same

mass. So, the total mass of products is equal to the total mass of reactants. And this is law of conservation of mass.

• According to his theory, the number and kinds of atoms are constant in a given compound. Since, this is true, therefore, a compound will always have the same elements combined together in the same proportion by mass. And this is law of constant proportions.

Drawbacks of Dalton’s atomic theory – It is now known that some statements of his theory are not correct. These are:

(i.) Atoms were indivisible according to Dalton. We now know that under special circumstances, atoms can be further divided into still smaller particles called electrons, protons and neutrons.

(ii.) Dalton’s atomic theory says that all the atoms of an element have exactly the same mass. It is, however, now known that atoms of the same element can have slightly different masses as in isotopes.

(iii.) His theory says that atoms of different elements have different masses. It is, however, now known that even atoms of different elements can have the same mass as in isobars.

Self Assessment

Answer the following questions in your notebook:

Q1. Which postulates of Dalton’s atomic theory is a result of law of conservation of mass? Q2. Which law of chemical combination deals with the composition of compound? Q3. Justify the statement, it is not possible to have an atom of compound. Q4. Hydrogen and oxygen combine in the ratio of 1:8 by mass to form water. What weight of oxygen gas would be required to completely react with 3g of hydrogen gas? Q5. According to Dalton’s atomic theory ,atom is indivisible. Is it true or not? Give reason. Q6. Mention the postulates of Dalton’s atomic theory. Q7. Give any two limitations of Dalton’ atomic theory. Q8. Show that the data given below is in agreement with the law of constant proportions:

Substance Experiment 1 Experiment 2 Experiment 3 Iron/g 2.78 3.05 4.49

Iron oxide/g 4.00 4.36 6.42 Q9. When 3.0 gm of carbon s burnt in 8.0 gm oxygen, 11.0 gm of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.0 gm of carbon is burnt in 50.00 gm of oxygen ? Which law of chemical combination will govern your answer ? Q10. State the law of conservation of mass. HELPLINE Ms Dhara Kalra 9871523848

Delhi Public School Ghaziabad Vasundhara SUBJECT : ECONOMICS

CLASS : IX

CH-3 (Poverty as a Challenge) OBJECTIVES:

1. To recall the concept of poverty. 2. To understand the meaning of poverty as per social scientists. 3. To describe social exclusion. 4. To explain the concept of vulnerability. 5. To discuss the concept of poverty line.

CONCEPT OF POVERTY This chapter deals with one of the most difficult challenges faced by independent India—poverty. In our daily life, we come across many people who we think are poor. They could be landless labourers in villages or people living in overcrowded jhuggis in cities. They could be daily wage workers at construction sites or child workers working in dhabas. Do you have any idea as to what is the extent of poverty in India? In fact, every fourth person in India is poor. This means, roughly 260 million (or 26 crore) people in India live in poverty. This also means that India has the largest single concentration of the poor in the world. This illustrates the seriousness of the challenge. Read the two typical cases of poverty (urban and rural case) from the text book on pg nos. 29 and 30. You must have drawn certain conclusions on the basis of your reading. Read para 1, column 1 on pg 31 and answer the following question in your notebook. Q.1. What do you mean by poverty? However, the definition of poverty has many facets. Social scientists look at it through a variety of indicators. Read para 3, column 1 on pg 31 and mark the indicators used by social scientists and attempt the following question in your notebook. Q.2. How do social scientists define poverty? CONCEPT OF SOCIAL EXCLUSION According to this concept, poverty must be seen in terms of the poor having to live only in a poor surrounding with other poor people. Read para 4, column 1 and 2 on pg 31. CONCEPT OF VULNERABILITY Vulnerability to poverty is a measure, which describes the greater probability of certain communities (say, members of a backward caste) or individuals (such as a widow or a physically handicapped person) of becoming, or remaining, poor in the coming years.

Read para 2, column 2 on pg 31. CONCEPT OF POVERTY LINE Each country uses an imaginary line that is considered appropriate for its existing level of development and its accepted minimum social norms. This imaginary line is called the poverty line. Poverty line may vary with time and place. For example, a person not having a car in the United States may be considered poor. In India, owning of a car is still considered a luxury. While determining the poverty line in India, a minimum level of food requirement, clothing, footwear, fuel and light, educational and medical requirement etc. are determined for subsistence. The present formula for food requirement while estimating the poverty line is based on the desired calorie requirement. Food items such as cereals, pulses, vegetable, milk, oil, sugar etc. together provide these needed calories. The calorie needs vary depending on age, sex and the type of work that a person does. The accepted average calorie requirement in India is 2400 calories per person per day in rural areas and 2100 calories per person per day in urban areas. Read pg nos. 31 and 32 for the concept of poverty line and answer the following questions in your notebook. Q.1. What is the definition of poverty line in India on the basis of:

(a) Average calorie requirement (b) Monthly Income

Q.2. Why do different countries use different poverty lines? Q.3. What do you think would be the “minimum necessary level” in your locality? CAUSES OF POVERTY

Causes of

poverty

Unemployment Child labour

Illiteracy Poor health/maln

utrition

Answer the following multiple choice questions:

1. Who said that India would be truly independent only when the poorest of its people become free of human suffering?

(i) Jawaharlal Nehru (ii) Mahatma Gandhi (iii) Indira Gandhi (iv) Rajiv Gandhi

2. Which organization conducts sample surveys for estimating the poverty line in India? (i) National Statistical Organisation (ii) National Sample Survey Organisation (iii) Economic Survey (iv) Ministry of Finance

3. Which state of India has the highest percentage of people below the poverty line?

(i) Bihar (ii) Madhya Pradesh (iii) Orissa (iv) Assam

4. The accepted average calorie requirement in India in rural areas is:

(i) 2100 calories per person per day (ii) 2200 calories per person per day (iii) 2300 calories per person per day (iv) 2400 calories per person per day

5. On the basis of monthly income, in year 2000 in urban areas, poverty line was fixed at:

(i) Rs. 328 per month per person (ii) Rs. 454 per month per person (iii) Rs 1640 per month per person (iv) Rs. 2270 per month per person Helpline Number : 9818709900

Delhi Public School Ghaziabad Vasundhara SUBJECT : FRENCH

CLASS : IX Leçon-6 LA RENTRÉE Learning Objectives : You will be able to : 1.Write and use possessive adjectives in french. (Do the Ex in the French notebook) Complétez avec l’adjectif possessif :- (mon,ma,mes,ton,ta,tes,notre,nos,votre,vos,leur,leurs)

(i) je vais à l’école avec __________ amis. (ii) Manuel met __________ livres dans __________ cartable.

(iii) Nous rangeons __________ vêtements dans l’armoire.

(iv) Tu écris une lettre à_______ tante ou à _________ oncle?

(v) _________ cousins arrivent aujourd’hui.

(vi) _________ grand-père est vieux._______ cheveux sont blancs.

(vii) Les enfants aiment _______ parents.

(viii) Est-ce-que tu prends _________ dîner avec_______ famille.

(ix) Marie va au cinéma avec ________ soeur et _______ famille.

(x) Vous parlez souvent à ________ enfants?

(xi) Quel est le nom de __________ neveu?

(xii) Valerie est la fille de _________ professeur.

(xiii) Tu achètes un cadeau pour ________ petite-amie?

(xiv) Julienne est ________ cousine.

(xv) La voisine de M.Dubois est _______ copine.

(xvi) Sophie attend _______ amis devant le cinéma.

(xvii) C’est _______ sac; où est _______ sac.

(xviii) Je pars en vacances avec _________ amie.

(xix) Vous placez _________ livres dans l’armoire.

(xx) Le professeur parle à_________ étudiants.

Helpline Number : 9810026311

Delhi Public School Ghaziabad Vasundhara SUBJECT: GEOGRAPHY

Class : IX CH.4 - CLIMATE

Students, today we are going to learn about the climate and other things related to climate; specially the climate of India.

So, why do we have to learn about it now?

Well; to learn and understand the different climatic conditions prevailing in

different parts of India.

So let’s start – How is weather today? Is it cloudy? Or hot? Or pleasant?

(Write your answer in the notebook)Here you may get different answers

throughout the day.

This is because weather keeps on changing in shorter duration.

So, what is weather? Refer to pg. no. 26 of your textbook & write down

answer in the notebook.

Now read pg no 26 of your textbook and answer the following questions.

Do not forget to write your answers in notebook.

1. Define climate.

2. What is ‘monsoon?’

3. Write down annual precipitation on Meghalaya and Ladakh.

4. What is the origin of the word ‘monsoon?’

Well you must have seen that climate differs from place to place. Why is it so? To

find out the answer we have to have a look at the following GO.

Now read pg no 27 of your textbook. Can you elaborate on the six climatic

controls given in the GO? I will do one for your benefit.

Latitude: - Due to the curvature of the earth, the amount of solar energy

received varies according to the latitude. As a result, air temperature decreases

from the Equator towards the Poles.

Major controls of the

Latitude, Altitude, Wind & Pressure system

Distance from the sea, Ocean Currents, Relief Features

Latitude – a) Tropic of Cancer divides the country into almost equal.

b) Area lying to the South of the tropic belongs to the tropical climatic

region.

c) The remaining area to the North of the tropic comes under

subtropical

climatic region.

Altitude - a) India has mountains as well as coastal areas.

b) The Himalayas prevent cold winds from central Asia from entering

the

Sub-continent.

c) We experience milder winters compare to central Asia because of

the

Himalayas.

Pressure & Winds - a) Pressure & surface winds

b) Upper air circulation

c) Western cyclonic disturbances & tropical cyclones.

Now read pg no 27 and 28 of your textbook and answer the following questions.

Do I need to tell you that you have to write your answers in the notebook?

• What are Jet Streams? (3)

• Define Coriolis force. (3)

• Write a short note on ‘Western cyclonic disturbances’. (4)

• Define the wind & pressure condition during winter and summer. (4)

• Who were the first people to discover the phenomena of monsoon? (1)

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Ok, now elaborate remaining five climatic controls the in the same way.

Now, we will see the factors affecting India’s climate.

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Delhi Public School Ghaziabad Vasundhara

SUBJECT : HISTORY CLASS : IX

History: - Ch.6 – Peasants & Farmers

Students, today we are going to learn about the beginning of modern agriculture in three countries: England, USA and India.

So, why do we have to learn about it now?

Well; we are discussing about it as this is where the revolution for modern

agriculture started. So first we will discuss about England – the place where it all

started.

To begin with, read first paragraph on pg no 124 of your textbook. Who was

Capt. Swing? Right your answer in notebook.

Our first topic is ‘The coming of modern agriculture in England’

Ok, now let’s see the condition of English country side in early 18th century.

• Country side was not enclosed into privately owned property.

• Peasants cultivated the land around the village.

• Every villager was allotted some strips, fertile as well as non-fertile.

• This land was given in the public meeting at the beginning of the year.

• This land was known as ‘The Common Land’.

Now read pt.1.1 from pg no 124 and add on remaining features of the common

land to complete the GO and copy it in your notebook. (There should be at

least 4 more points.)

Were you able to do it? Good!

But you know, this ideal situation did not last long as selfish & rich farmers

wanted more prosperity for them & they demanded certain things.

Features of common land

It was accessible to all villagers for them to graze their cows.

People could collect fuel wood for fire & pick berries and fruits for food.

Find out these demands by reading pg no 125 of your textbook. Do you know

these demand has a particular name to it? …….. It is known as ‘Enclosure

Movement’.

Started in late 17th century gained momentum after the mid-18th

century

Between 1750 & 1850, 6 million acres British Parliament too supported

this

Of land was enclosed. Process & passed 4,000 Acts to

Legalize these enclosures.

1. Increasing population & increasing demand for food grains led to

enclosure movement in England.

2. The rising prices of agricultural products like wool, wheat, meat, milk,

fruits in the world market also helped in spread of enclosure

movement.

3. In 19th century enclosure were seen necessary to make long term

investments on land & plan crop rotation to improve soil.

4. Enclosures also allowed richer landowners to expand the land under

their control and produce more for market.

5. The coming of modern agriculture & technology also helped

enclosure movement in England.

��

Well, there were quite a few reasons. I am writing them here, just go through them & remember them. Also copy them in notebook.

But even with the increasing population, England was

producing 80% of its food. Farmers & landlords resorted to

the following measures to increase production.

• By bringing new land under cultivation.

• They took over forest commons and marshes &

converted them into cultivated land.

• They continued using simple innovations in

agriculture.

• They started growing Turnips and Clover.

• They discovered that planting these crops improved the soil and made it

more fertile.

So, now that you know the reasons behind ‘Enclosure Movement’ we will see

how it affected poor farmers in England and how did they retaliate.

• Poor farmers lost their mean of livelihood as they were heavily dependent

on common land.

• They had to work on the farms of rich land owners as labourers & paid poor

wedges.

• Introduction of new technology & machinery resulted in labourers losing

their work.

• The poor were displaced from the land where enclosing took place.

• For a very large part of the year the poor had no work.

Now based on your reading of above text & pg no 128 and 129 of your

textbook, answer the following questions. You can also refer to textbook for more

elaborate answers.

Q1. How did food production increase with rising population?

Q2. ‘The introduction of threshing machine indicated bad times for the poor’.

Justify the statement.

Q3. State the changes happened in England with the arrival of modern

agriculture.

Q4. Who was Capt. Swing?

Q5. Draw a timeline marking important events on the topic “the coming of

modern agriculture in England”.

Help line- Ms.Kanupriya -9310275779 Ms.Sonal Deshpande-9311493999

Delhi Public School Ghaziabad Vasundhara

Subject: Mathematics Class IX

Chapter: Surface Area & Volume

Contents: a) Surface Area

b) Volume

c) 3- Dimensional Objects

d) Surface Area & Volume of Cylinder

e) Surface Area & Volume of Cone

f) Surface Area & Volume of Sphere

g) Surface Area & Volume of Hemisphere

Dear Students, we will try to cover a),b),c),d) and e) of the above mentioned contents through this presentation. Time requires : 4 – 5 hrs. ( 20-30 min each day) Learning Objectives: You will be able to :

• Understand the concept of area and volume

• Understand and apply various formulas to solve real life problems related to cylinder,

cone and sphere.

Are we ready?? Lets begin with some pre requisite: Q1. What is Surface area? Ans. The area occupied by the surfaces of an object is called its surface area.

For example: We all must have seen a dice. A dice is a cubical shaped object(generally used to play LUDO). How many surfaces does it have? Answer is : 6

Now, we know that there are 6 square faces, each of area-(side)2. So six sides will have area:

(side)2+(side)2+(side)2+(side)2+(side)2+(side)2=6(side)2

This is called the surface area of a dice or a cube. (The area covered by all the sides)

Q2. What is volume? Ans: The volume is the space occupied by an object. For example: If we wish to find the volume of the same cube. Volume is (length) X (breath) X (Height) Now in cube the volume is (side)X(side)X(side) = (side)3

In this chapter we are going to learn about CYLINDER, CONE And SPHERE First we will understand CYLINDER

CYLINDER A Right Circular Cylinder If we revolve/fold a rectangular sheet of paper either length wise or breadth

wise (as shown in figure). The figure we get is a cylinder. Surface area of the cylinder: (L.S.A)Lateral/Curved Surface area is : 2rh (T.S.A)Total Surface area : 2rh+ 2 r2 (C.S.A + area of 2 circles) = 2r(h + r) Volume: = r2h

Example1: A cylindrical can has a base radius 7 cm and height 10 cm, find the

L.S.A , T.S.A and volume of the can. Solution: r = 7 cm h = 14 cm For C.S.A = 2rh Putting the values we get: 440 cm2 Now for T.S.A: 2r(h + r) T.S.A = 2 (7)(10 +7) T.S.A =

T.S.A = 748 cm2 Now for volume: r2h V =

V= 1540 cm2 Now try Yourself: Q1. Find the volume and curved surface area of a cylindrical tank of radius 70

cm and height 140 cm. Q2. Find the volume of the liquid packed in a cylindrical beaker of diameter

14cm and height 100 cm. Q3. If the curved surface area of a right circular cylinder is 440 cm2 and height

is 10cm, find the Volume.

Now let us try another example: Example 2: An open cylinder of radius 10 cm and height 21 cm has to be made,

find the cost of the sheet required to make such cylinder if 1cm2 sheet cost Rs. 10.

Solution: Now, since it is an open cylinder that means that the top circle is missing that is:

There is a curved surface and a circle at the base. Top circle is missing. So the area of the sheet required will be: 2rh + r2 Area = ( )+ ( )

Area = 1634 cm2 Now the cost = Rs 101634 = Rs. 16340.

Now try yourself: Q1. An open cylinder of radius 20 cm and height 70 cm has to be made from

a sheet. Find the cost of the sheet required to make such a cylinder at Rs. 12 per cm2.

Q2. A rectangular sheet of dimensions 88 cm by 44cm is rolled along its breath, find the curved surface area of the cylinder so formed.

(If it would have been revolved along length, will the S.A changes? Why???) Now, Let us take another example: Example 3: A cylindrical beaker of radius 10 cm and height 14 cm is full of

water, if the water is transferred to another cylindrical beaker of radius 7 cm, find the level of water in the beaker. Solution: We know, when we transfer/ melt any solid to form another, the volume of the substance remain same.

In this case the liquid has been transferred so, the volume of the water will remain same.

Volume: = r2h V =

On solving the above equation h = 28.5 cm

Example 4: A cylindrical road roller of diameter 1m and length 2 m takes 100 revolutions to cover certain area. Find the area covered by it.

Solution: The area covered by a road roller = C.S.A of the roller (as only the curved surface is in contact with the ground)

C.S.A = = 2rh C.S.A =

C.S.A = 2.68 m2 The area covered by 1 revolution = 1 C.S.A So the area covered by 100 revolutions will be: 100 1 C.S.A Area = 100 Area = 268 m2 Now try yourself: Q1. A cylindrical road roller of radius 35 cm and length 1 m takes 500

revolutions to cover certain area find the area covered by it. Q2. A cylindrical beaker of radius 20 cm and height 100 cm is full of liquid

chocolate. If this chocolate is to be filled in small cylindrical containers of radius 1 cm and height 1 cm, find the approximately how many such containers can be filled.

Q3. A cylindrical candle of radius 14 cm and length 35 cm is melted to form another cylindrical candle of radius 7 cm, find the length of this candle.

Now we will study CONE:

CONE

Cone Volume of a Cone =

Lateral / Curved Surface Area = rl Where l = T.S.A = rl + r2 Now lets take an example: Example 5: A cone(without base) of radius 3 cm and height 4 cm has to made. Find the area of the metal sheet required. Also find the Volume of liquid this cone can keep. Solution: r = 3 H = 4 Now using Pythagoras th. We can find l l =

l = l = 5 cm Hence the area = rl C.S.A =

C.S.A = 47.1 cm2

Now for the volume: V =

V=

V = 37.7 cm3 Now try Yourself: Q1. A cone of height 12 cm and base radius 5 cm has to be made. Find

the cost of metal used if 1 cm2 cost Rs 20. Also find the amount of water it can hold.

Q2. If the radius of a right circular closed cone is 12 cm and the height is 5 cm. Find the T.S.A. Q3. The cone of radius 12 cm and height 21 cm is full of water. If this water is transferred to a cylinder of radius 6 cm, find the height of the water level in this cylinder. Q4. A joker’s cap is in the form of a cone of diameter 14 cm snd height 7 cm. Find the cost of sheet required to make 100 such caps if 1 cm2 cost Rs 10.

Helpline: Ms. Rinkoo Narayan( 9818030097); Mr. Gaurav Bedi (9810244494)

DELHI PUBLIC SCHOOL GHAZIABAD VASUNDHARA SUBJECT: PHYSICS

CLASS: IX CHAPTER-GRAVITATION

Topic: - Archimedes’ Principle Core Objectives: 1. To appreciate the discovery of Archimedes' principle. 2. To realize the importance and need to know effect of Archimedes principle. Learning Objectives: You will be able to: 1. State the discovery of Archimedes' Principle. 2. Name the force exerted by fluid on the immersed objects. 3. Explain the concept of Archimedes' Principle. 4. Verify the Archimedes principle experimentally. 5. Enumerate the factors affecting buoyant force. 6. Write three applications of Archimedes' Principle. It is a matter of common experience that bodies appear lighter when immersed in water or any other liquid. While bathing we notice that the mug of water suddenly appears heavier as soon as it comes above the water surface. Similarly, when a fish is pulled out of water, it appears to be heavier in air than inside the water. Now let us see why it is so. Objects appear to be less heavy in water or in any liquid because the liquid or water exerts an upward force on the objects immersed in it. Discovery of Archimedes' Principle Once upon a time, there was once a king named as Hiero of Syracuse. He made a crown out of gold and wanted to test whether his goldsmith had done any trickery in it. Archimedes doubted whether the goldsmith had kept a pound of gold with himself and added brass or silver in its place. He was thinking a question while he was getting ready for a bath. A big bowl or tub was full of water up to the edge, and as the king enters in the tub, the quantity of water flowed outside the tub and spread on the floor. The same event had happened a hundred times before, but this was the first time when Archimedes had thought why this happened. Introduction to Archimedes' principle He had noticed that he had displaced the same bulk of water as much as he weighed. Then the idea crept his mind. Gold is heavier when compared to silver. Ten pounds of pure gold is not as bulky as the mixture of seven pounds of gold and 3 pounds of silver. If king Hiero’s crown is made of pure gold it will displace the same amount of water as any other ten pounds of pure gold. But if it is made of partly gold and partly silver it will displace a larger amount of water. Now the crown was tested. It was found that the crown displaces much more water than the amount of water displaced by ten pounds of pure gold. So that the goldsmith was proved dishonest. Click on the embedded file (highlighted in yellow color). You need to have a real player downloaded on your system to view this file. Opening may take some time.

�� Archimedes' Principle Archimedes' studied the upthrust acting on a body, when it is partially or completely immersed in a fluid by performing several experiments and then stated the following principle known as the Archimedes' Principle. According to this principle, when a body is partially or wholly immersed in a fluid, it experiences an upthrust (buoyant force) equal to the weight of the liquid displaced. The fluid displaced by the submerged body has a weight W=mg. The mass can now be expressed in terms of density and volume. M = pV , where m is mass, p (read as rho) is the density and V is the volume. The force that pushes upwards the object immersed in water is the force of buoyancy. Thus the upward force acting on an object immersed in a liquid resulting in the apparent loss of weight of the object is called the buoyant force. The tendency of a liquid to exert an upward force on an object placed in it thereby making it float or rise is called buoyancy. Apparent Weight of the Body The apparent weight of the body is equal to the weight of the body experienced in the liquid when it is dipped in the liquid. Apparent weight of the liquid = True weight of the body - Loss in the weight of the body In other words Apparent weight = True weight - Buoyant force Example for Archimedes Principle If the weight of a sphere is 26 g in air and loss in the weight of the sphere is 16 gm so the Apparent weight of the sphere = Weight of the sphere in air - loss in the weight of the sphere = 26 - 16 = 20 gram force Now by performing an experiment let us find out whether there is an apparent loss of weight when immersed in water. Experiment to Verify Archimedes' Principle Take a clean and dry beaker and find it's mass (m) using a physical balance. Now take a stone and find the weight of a stone by suspending it from a spring balance. Suspend the spring balance as shown in the figure.

Note the reading on the spring balance. Let it be W1. Fill an Eureka can (Eureka can is a beaker having a spout near the top) with water filled till the spout. Place the beaker of mass 'm' under the spout. Now, slowly dip the stone in the water in a container and note the reading on the spring balance. The reading shown on the spring balance goes on decreasing until it is completely immersed in water. The reading on the spring balance gives us the weight of the stone. When the stone is immersed in water it displaces a certain amount of water. The spring balance records lesser value thereby showing that the solid experiences an upthrust. The displaced water is collected in the beaker. Using the physical balance the mass of the water and beaker is determined. Let it be m1.

Since the reading goes on decreasing, we can infer that the weight of the object is decreasing when it is lowered in water. The apparent loss of weight shows that a type of force is acting on the object in the upward direction thereby decreasing the weight. If we compare the apparent loss of weight of the solid in water, with the amount of water displaced, it is found that they are equal. This experiment thus verifies Archimedes' Principle. Factors Affecting the Buoyant Force We know that when an iron nail is placed on the surface of water it sinks whereas ship made up of iron floats. This is because size or volume of the ship is more. Similarly when an iron nail and a cork of some mass is placed on water, the iron nail sinks because the density of iron nail is more than the density of water and whereas density of the cork is less than that of the water. Thus if the density of the liquid is more than the density of the material of the body then the body floats due to the buoyant force exerted by it and vice-versa. From the above examples we can infer that the buoyant force experienced by a body when submerged in a liquid depends on the volume of the body and the density of the liquid. Application of Archimedes' Principle It is used in designing ships and submarines. The lactometers and hydrometers used for measuring the purity of a sample of milk and for determining the density of the liquids are based on this principle.

Submarines A submarine sinks by taking water into its buoyancy tanks. Once submerged, the upthrust is unchanged, but the weight of the submarine increases with the inflow of water and it sinks faster. Compressed air is used to blow water out of the tanks when it has to resurface.

(An atomic submarine. This remains underwater for weeks without surfacing). • Balloons filled with hot air or hydrogen, weigh less than weight of cold air that it displaces. Therefore, the

upthrust is greater than its weight and the resultant upward force on the balloon, causes it to rise.

• Hydrometer is used to measure relative density of a liquid. It consists of a weighted sealed glass tube and

a scale and when placed in the liquid, the scale reads the level of the liquid surface. In a denser liquid, the scale floats since less liquid is displaced. The weight of the displaced liquid is equal to its own weight, the number on the scale therefore, increases downwards. This method is use to check the state of a car battery. In a fully charged medium, the R.D of the acid should be 1.25 and recharging is required when reading is less than 1.8.

Know more • Pressure is a scalar quantity, because its direction is unique (normal to the area) and not to be specified. • Barometer uses mercury. This is because, if water were used, then a longer glass tube would have to be used

(10m, since10m of water column is required to balance the atmospheric pressure.). Also water sticks to the glass tube.

• Blood pressure is measured in mm of Hg. The systolic pressure is 120mm of Hg and the diastolic pressure is 80mm of Hg.

• The thrust on the total area of the body of a man of a medium built (1.5m2) is 1.5 ton weight. How is he able to withstand this thrust? This is because there is a large number of opening and pores in the skin, through which air enters the system and presence of air inside, counterbalances the pressure outside.

• Pressure outside the human body changes at high altitudes or undersea. Therefore, precautions are to be taken to compensate for these differences.

Given below are Q & A on the topic ‘Archimedes' Principle’

Read and write these carefully in your independent practice notebook.

Q 1. Name the force experienced by the body when it is immersed in a liquid. Ans. Buoyant force is experienced by the body when it is immersed in a liquid. Q 2. Iron nails sinks in water.Why? Ans. The density of an iron nail is more than the density of water. This means that the upthrust of water on iron nails is less than the weight of the nail. So it sinks. Q 3. What do you mean by force of buoyancy? Ans. When a body is completely or partially immersed in a fluid, then the upward thrust acting on the body is called force of buoyancy. Q 4. State Archimedes’ principle. Ans. Archimedes’ principle states that when a body is immersed partially or fully in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it. Q 5. The density of gold is 19.3 103 kg/m3. Find its relative density.

Ans. Q 6. Why fluid exert pressure ?How is the pressure transmitted in a fluid? Ans. As fluids have weight , they exert pressure on the base and walls of the container they are enclosed . In a confined mass of fluid, pressure applied on the fluid in any particular direction is transmitted undiminished (i.e. equally)in all directions. Q 7. What are two main factors on which the buoyant force depends? Ans. Two main factors on which the buoyant force depends are: (i) Density of the fluid. (ii) Value of acceleration due to gravity at that place. Q 8. Explain why iron nail sinks in water, but a ship made up of iron floats? Ans. If we place an iron nail on the surface of water, it sinks. This is because the density of iron is greater than that of water, so the weight of the nail is more than the upthrust of the water on it. On the other hand a ship made of iron does not sink. This is because the ship is hollow and the empty space contains air which makes the average density of the ship less than that of water. Thus, even with a small part of its submerged into water, the weight of the water displaced becomes equal to the total weight of the ship and hence the ship floats.

Self Assessment Sheet Answer the following questions in your notebook: Q1. Choose the most appropriate answers:

i) Fluids are

a. Solids and liquids b. solids and gases c. liquids and gases d. none of the above

ii) Pressure exerted by a liquid on a container (in which it is enclosed) acts on a. the base of the container b. the walls of the container c. both base and walls of the container d. none of the above iii) Every liquid exerts an upward force on the objects immersed in it. Upward force is called

a. gravitational force b. magnetic force c. buoyant force d. mechanical force

iv) Buoyant force acting on an object is equal to the

a. mass of the solid immersed b. weight of the solid immersed c. mass of the liquid displaced by object d. weight of the liquid displaced by object v) An iron ball and a wooden ball of the same radius are released from the same height in the vacuum. The time

taken by both of them to reach the ground are; a. not equal b. roughly equal c. exactly equal d. zero vi) All bodies whether large or small fall with the; a. same force b. same acceleration c. same velocity d. same momentum vii) The force experienced by a body when it is immersed in a liquid a. Magnetic force b. Electrostatic force c. Buoyant force d. None of these. viii) The weight of a body at the centre of the earth is a. zero b.infinite c. same at other places d. slightly greater than that at poles ix) When an apple falls from a tree a. only earth attracts the apple b. both the apple and earth attract each other c. Both d. None. x) Iron nail a. float in water b. sinks in water c. dissolves in water d. none.

Q2. Which of the two will double the pressure- doubling the area or making the area half? Q3. Can a body have mass but no weight? Q4. What is weightlessness? Give two examples. Q5. It is easier to lift a heavy stone under water. Give reason. Helpline: Ms. Geetali Grover (9873654756)

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