Ch.03 . Diversity in living things and their classification

Page No 25:

Question 1:

Match the pairs.

A Group	B Group
(a) Amphibian	(1) A Monkey
(b) Vertebrate	(2) A Snake
(c) With scales	(3) A Frog

ANSWER:

A Group	B Group
(a) Amphibian	(3) A Frog
(b) Vertebrate	(1)A Monkey
(c) With scales	(2) A Snake

Page No 25:

Question 2:

Who is the odd one out ?
(a) Fungus, mushroom, chrysanthemum, spirogyra
(b) Mango, banyan, palm, chick pea
(c) Grape, orange, lemon, hibiscus
(d) Sunflower, banyan, jowar, bajra
(e) Guava, radish, carrot, beetroot
(f) Deer, fish, man, worms

ANSWER:

(a) Fungus, mushroom, chrysanthemum, spirogyra- Chrysanthemum is the odd one out because it is a flowering plant whereas rest of them are non flowering.

(b) Mango, banyan, palm, chick pea- Chick pea is the odd one out because it is a type of herb whereas rest of them are types of trees.

(c) Grape, orange, lemon, hibiscus- Grape is the odd one out because it is a climber while rest of them are shrubs.

(d) Sunflower, banyan, jowar, bajra- Banyan is the odd one out because it is a perennial plants whereas rest of them are annual plants.

(e) Guava, radish, carrot, beetroot- Guava is the odd one out because it is a perrenial plant whereas rest of them are biennial plants.

(f) Deer, fish, man, worms- Worm is the odd one out because it is an invertebrate whereas rest of them are vertebrates.

Page No 25:

Question 3:

What is the difference ?
(a) Flowering plants – non-flowering plants
(b) A tree – a shrub
(c) Vertebrates – invertebrates

ANSWER:

a. 

Flowering Plants	Non-flowering Plants
They have flowers and produce seeds and fruits.	They do not produce flowers, seeds, and fruits
They have structures like roots, stems and leaves.	They amy or may not have structures like roots, stems and leaves.
Ex- Tulip and Mango	Ex- Ferns and Mosses

b. 

Trees	Shrubs
1. Plants which grow very tall and have strong, hard stems or trunks are called trees.	Plants which grow upto a medium height are called shrubs.
2. They have branches which are at some height above the ground.	They have branches which are very close to the ground.
3. Mango tree, neem tree etc.	Oleander, hibiscus etc.

c. 

Vertebrates	Invertebrates
They have a backbone made up of vertebrae.	They do not have a backbone.
They can be cold blooded or warm blooded.	They are always cold blooded.
They have a well developed brain.	They do not have a well developed brain.
Example: frog and lizard	Example: Earthworm and snail

Page No 25:

Question 4:

True or false ?
(a) The snail is an aquatic animal.
(b) Amphibians can live in air and in water.
(c) The function of the brain is well developed in vertebrate animals.
(d) The amoeba is a multicellular animal.

ANSWER:

(a) The snail is an aquatic animal.- False
(b) Amphibians can live in air and in water.- False
(c) The function of the brain is well developed in vertebrate animals.- True
(d) The amoeba is a multicellular animal.- False

Page No 25:

Question 5:

Write two names of each.
(a) A flowering plant
(b) A non-flowering plant
(c) A tree
(d) A shrub
(e) A creeper
(f) An annual plant
(g) A biennial plant
(h) A perennial plant

ANSWER:

(a) A flowering plant- Rose and lotus
(b) A non-flowering plant- Ferns and mosses
(c) A tree- Mango and neem
(d) A shrub- Lemon and henna
(e) A creeper- Money plant and cucumber
(f) An annual plant- Marigold and corn
(g) A biennial plant- Carrots and parseley
(h) A perennial plant- Asparagus and artichoke

Page No 25:

Question 6:

Write answers to the following.
(a) What are the parts of a plant ?
(b) What are the functions of the root ?
(c) Why is it necessary to classify living things ?
(d) What are the criteria used to classify living things ?
(e) Tell some characteristics of creepers.
(f) Explain the characteristics of herbs with two examples.
(g) On the basis of which criteria will you classify plants and animals ?
(h) What protects the bodies of animals?

ANSWER:

Ans 6 a. The various parts of a plants are:

• Roots: They absorb water and minerals from the soil and also anchor the plant firmly in the soil.
• Stems: Spread out branches to bear leaves, flowers and fruits, conducts water and minerals to different plant parts and performs functions of storage, support, protection and vegetative propagation.
• Leaf: They are called ‘food factories’ of a plant. They carry out photosynthesis, a process by which they synthesize their food.
• Flower:  In plants, flower is the functional unit concerned with the sexual reproduction of plants.
• Fruits: They have different shapes and contain one or more seeds.

b. The functions of the roots are as follows:

• they help in anchoring the plant to the soil.
• they also help in the absorption of water and nutrients from the soil.

c. Importance of classification:

(i) Classification ensures uniformity. All life forms can be studied on a common platform.

(ii) Classification ensures the study of interrelationship between various groups.

(iii) It helps us to study many organisms at same time.

d. Organisms can be classified on the basis of similarities and differences in their structure, their organs and other characteristics.


e. Plants which cannot stand upright, and spread on the ground are called creepers. They show characteristics like:

• their stem is very flexible, soft and green
• it grows rapidly with the help of a support

f. Herbs have the following characteristics:

• they grow upto the size 1-1.5 metres
• they have green and flexible stems
• they can live upto few months or upto two years
• examples of herbs include tulsi, parsley, mint etc.

g. Plants and animals are classified on the basis of different characteritics:

Plants are classified on the basis of 

• height
• shape of stems
• period of life cycle
• habitat

Animals are classified on the basis of:

• cell structure
• vertebral coloumn
• method of reproduction
• habitat

h. There are different mechanisms by which animals protect themselves from danger such as their predators:

• Some organisms are covered by hard shells to protect themselves. For example, garden snail, tortoise etc. have a heard shell which they use to hide themselves under danger conditions.
• Star fish and porcupines have spines on their surface which they can use against their enemies.
• Organisms like chameleon and frogs can change their colours according to the surrounding environment. It is known as chamouflaging.
• Animals which are found in very cold regions have a thick layer of fat under the skin and thick fur to protect them from extreme cold conditions.

Page No 25:

Question 7:

Draw figures.
Draw the figure of a plant to show the parts, namely, the root, stem and leaves in it.

ANSWER:

Joint Bar Graph

Page No 53:

Question 1:

The number of saplings planted by schools on World Tree Day is given in the table below. Draw a joint bar graph to show these figures.

School Name	Name of sapling	Almond	Karanj	Neem	Ashok	Gulmohar
Nutan Vidyalaya		40	60	72	15	42
Bharat Vidyalaya		42	38	60	25	40

ANSWER:

The required joint bar graph is shown below.

Page No 53:

Question 2:

The table below shows the number of people who had the different juices at a juice bar on a Saturday and a Sunday. Draw a joint bar graph for this data.

Days	Fruits	Sweet Lim	Orange	Apple	Pineapple
Saturday		43	30	56	40
Sunday		59	65	78	67

ANSWER:

The required joint bar graph is shown below.

Page No 54:

Question 3:

The following numbers of votes were cast at 5 polling booths during the Gram Panchayat elections. Draw a joint bar graph for this data.

Persons	Booth No.	1	2	3	4	5
Men		200	270	560	820	850
Women		700	240	340	640	470

ANSWER:

The required joint bar graph is shown below.

Page No 54:

Question 4:

The maximum and minimum temperatures of five Indian cities are given in °C. Draw a joint bar graph for this data.

Temperature	City.	Delhi	Mumbai	Kolkata	Nagpur	Kapurthala
Maximum temperature		35	32	37	41	37
Minimum temperature		26	25	26	29	26

ANSWER:

The required joint bar graph is shown below.

Page No 54:

Question 5:

The numbers of children vaccinated in one day at the government hospitals in Solapur and Pune are given in the table. Draw a joint bar graph for this data.

City	Vaccine	D.P.T. (Booster)	Polio (Booster)	Measles	Hepatitis
Solapur		65	60	65	63
Pune		89	87	88	86

ANSWER:

The required joint bar graph is shown below.

Page No 54:

Question 6:

The percentage of literate people in the states of Maharashtra and Gujarat are given below. Draw a joint bar graph for this data.

State	Year	1971	1981	1991	2001	2011
Maharashtra		46	57	65	77	83
Gujarat		40	45	61	69	79

ANSWER:

The required joint bar graph is shown below.

Ch.13.Pythagoras' Theoram

Question 1:

In the figures below, find the value of 'x'.

ANSWER:

(i)
  
In the right angled triangle LMN, ∠M = 90^∘. Hence, side LN is the hypotenuse.
According to Pythagoras' theorem,
l(LN)² = l(LM)² + l(MN)²
⇒(x)² = (7)² + (24)²
⇒x² = 49 + 576
⇒x² = 625
⇒x² = (25)²
⇒x = 25
∴ the value of x is 25.

(ii)

In the right angled triangle PQR, ∠Q = 90^∘. Hence, side PR is the hypotenuse.
According to Pythagoras' theorem,
l(PR)² = l(QR)² + l(PQ)²
⇒(41)² = (x)² + (9)²
⇒1681 = x² + 81
⇒x² = 1681 − 81
⇒x² = 1600
⇒x² = (40)²
⇒x = 40
∴ the value of x is 40.

(iii)

In the right angled triangle EDF, ∠D = 90^∘. Hence, side EF is the hypotenuse.
According to Pythagoras' theorem,
l(EF)² = l(ED)² + l(DF)²
⇒(17)² = (x)² + (8)²
⇒289 = x² + 64
⇒x² = 289 − 64
⇒x² = 225
⇒x² = (15)²
⇒x = 15
∴ the value of x is 15.

Page No 90:

Question 2:

In the right-angled ∆PQR, ∠ P = 90°. If l(PQ) = 24 cm and l(PR) = 10 cm, find the length of seg QR.

ANSWER:

In the right angled triangle PQR, ∠P = 90^∘. Hence, side QR is the hypotenuse.
According to Pythagoras' theorem,
l(QR)² = l(PQ)² + l(PR)²
⇒l(QR)² = (24)² + (10)²
⇒l(QR)² = 576 + 100
⇒l(QR)² = 676
⇒l(QR)² = (26)²
⇒l(QR) = 26
∴ Length of seg QR = 26 cm.

Page No 90:

Question 3:

In the right-angled ∆LMN, ∠ M = 90°. If l(LM) = 12 cm and l(LN) = 20 cm, find the length of seg MN.

ANSWER:

In the right angled triangle LMN, ∠M = 90^∘. Hence, side LN is the hypotenuse.
According to Pythagoras' theorem,
l(LN)² = l(MN)² + l(LM)²
⇒(20)² = l(MN)² + (12)²
⇒400 = l(MN)² + 144
⇒l(MN)² = 400 − 144
⇒l(MN)² = 256
⇒l(MN)² = (16)²
⇒l(MN) = 16
∴ Length of seg MN = 16 cm.

Page No 90:

Question 4:

The top of a ladder of length 15 m reaches a window 9 m above the ground. What is the distance between the base of the wall and that of the ladder ?

ANSWER:

Let LN be ladder of length 15 m that is resting against a wall. Let M be the base of the wall and L be the position of the window.
The window is 9 m above the ground. Now, MN is the distance between base of the wall and that of the ladder.
In the right angled triangle LMN, ∠M = 90^∘. Hence, side LN is the hypotenuse.
According to Pythagoras' theorem,
l(LN)² = l(MN)² + l(LM)²
⇒(15)² = l(MN)² + (9)²
⇒225 = l(MN)² + 81
⇒l(MN)² = 225 − 81
⇒l(MN)² = 144
⇒l(MN)² = (12)²
⇒l(MN) = 12
∴ Length of seg MN = 12 m.
Hence, the distance between base of the wall and that of the ladder is 12 m.

Page No 90:

Question 1:

Find the Pythagorean triplets from among the following sets of numbers.
 (i) 3, 4, 5
(ii) 2, 4, 5
(iii) 4, 5, 6
(iv) 2, 6, 7
(v) 9, 40, 41
(vi) 4, 7, 8

ANSWER:

It is known that, if in a triplet of natural numbers, the square of the biggest number is equal to sum of the squares of the other two numbers, then the three numbers form a Pythgorean triplet.

(i) The given set of numbers is (3, 4, 5).
The biggest number among the given set is 5.
5² = 25; 4² = 16; 3² = 9
Now, 16 + 9 = 25
∴ 4² + 3² = 5²
Thus, (3, 4, 5) forms a Pythagorean triplet.

(ii) The given set of numbers is (2, 4, 5).
The biggest number among the given set is 5.
5² = 25; 4² = 16; 2² = 4
Now, 16 + 4 = 20 ≠ 25
∴ 4² + 2² ≠  5²
Thus, (2, 4, 5) does not form a Pythagorean triplet.

(iii) The given set of numbers is (4, 5, 6).
The biggest number among the given set is 6.
6² = 36; 5² = 25; 4² = 16
Now, 25 + 16 = 41 ≠ 36
∴ 5² + 4² ≠  6²
Thus, (4, 5, 6) does not form a Pythagorean triplet.

(iv) The given set of numbers is (2, 6, 7).
The biggest number among the given set is 7.
7² = 49; 6² = 36; 2² = 4
Now, 4 + 36 = 40 ≠ 49
∴ 2² + 6² ≠  7²
Thus, (2, 6, 7) does not form a Pythagorean triplet.

(v) The given set of numbers is (9, 40, 41).
The biggest number among the given set is 41.
9² = 81; 40² = 1600; 41² = 1681
Now, 81 + 1600 = 1681
∴ 9² + 40² = 41²
Thus, (9, 40, 41) forms a Pythagorean triplet.

(vi) The given set of numbers is (4, 7, 8).
The biggest number among the given set is 8.
8² = 64; 7² = 49; 4² = 16
Now, 16 + 49 = 65 ≠ 64
∴ 4² + 7² ≠  8²

Page No 90:

Question 2:

The sides of some triangles are given below. Find out which ones are right-angled triangles?
(i) 8, 15, 17
(ii) 11, 12, 15
(iii) 11, 60, 61
(iv) 1.5, 1.6, 1.7
(v) 40, 20, 30

ANSWER:

It is known that, if in a triplet of natural numbers, the square of the biggest number is equal to sum of the squares of the other two numbers, then the three numbers form a Pythgorean triplet.

If the lengths of the sides of a triangle form such a triplet, then the triangle is right angled triangle.

(i) The sides of the given triangle is 8, 15 and 17.
Let us check whether the given set (8, 15, 17) forms a Pythagorean triplet or not.
The biggest number among the given set is 17.
(17)² = 289; 

(15)² = 225; (8)² = 64
Now, 225 + 64 = 289
∴ (15)² + (8)² = (17)²
Thus, (8, 15, 17) forms a Pythagorean triplet.
Hence, the given triangle with sides 8, 15 and 17 is a right-angled triangle.

(ii) The sides of the given triangle is 11, 12 and 15.
Let us check whether the given set (11, 12, 15) forms a Pythagorean triplet or not.
The biggest number among the given set is 15.
(15)² = 225; (11)² = 121; (12)² = 144
Now, 121 + 144 = 265 ≠ 225
∴ (11)² + (12)² ≠ (15)²
Thus, (11, 12, 15) does not form a Pythagorean triplet.
Hence, the given triangle with sides 8, 15 and 17 is not a right-angled triangle.

(iii) The sides of the given triangle is 11, 60 and 61.
Let us check whether the given set (11, 60, 61) forms a Pythagorean triplet or not.
The biggest number among the given set is 61.
(61)² = 3721; (11)² = 121; (60)² = 3600
Now, 121 + 3600 = 3721
∴ (11)² + (60)² = (61)²
Thus, (11, 60, 61) forms a Pythagorean triplet.
Hence, the given triangle with sides 11, 60 and 61 is a right-angled triangle.

(iv) The sides of the given triangle is 1.5, 1.6 and 1.7.
Let us check whether the given set (1.5, 1.6, 1.7) forms a Pythagorean triplet or not.
The biggest number among the given set is 1.7.
(1.7)² = 2.89; (1.5)² = 2.25; (1.6)² = 2.56
Now, 2.25 + 2.56  = 4.81 ≠ 2.89
∴ (1.5)² + (1.6)² ≠ (1.7)²
Thus, (1.5, 1.6, 1.7) does not form a Pythagorean triplet.
Hence, the given triangle with sides 1.5, 1.6 and 1.7 is not a right-angled triangle.

(v) The sides of the given triangle is 40, 20 and 30.
Let us check whether the given set (40, 20, 30) forms a Pythagorean triplet or not.
The biggest number among the given set is 40.
(40)² = 1600; (20)² = 400; (30)² = 900
Now, 400 + 900 = 1300 ≠ 1600
∴ (20)² + (30)² ≠ (40)²
Thus, (40, 20, 30) does not form a Pythagorean triplet.
Hence, the given triangle with sides 40, 20 and 30 is not a right-angled triangle.

Work and Energy.

Question 1:

Fill in each blank with the appropriate term from the brackets.
(a) A bucketful of water is to be drawn from a well. ....... will be done when a ......... is applied to do this, because there will be a ........... of water.
(displacement, work, force)
(b) If a ball is dropped on the sloping roof of a house, it acquires ...... and falls on the ground. That is, transformation of ........ energy into .......... energy takes place.
(kinetic, potential, motion)
(c) You might have seen some beautiful fireworks during Diwali. It is an example of transformation of ....... energy into....... energy.
(light, atom, chemical, solar)
(d) The solar cooker is an application of the ...... energy of the sun, while solar cells, solar lamps are applications of the ...... energy of the sun.
(light, chemical, heat)
(e) One labourer carried four pans of road metal through a distance of 100 metres. If he carries two pans of road metal through a 200 metre distance ......... work will be done.
(equal, more, less)
(f) The capacity that an object has for doing work is called ....... .
(energy, displacement, force)

ANSWER:

(a) A bucketful of water is to be drawn from a well. Work will be done when a force is applied to do this, because there will be a displacement of water.
(b) If a ball is dropped on the sloping roof of a house, it acquires motion and falls on the ground. That is, transformation of potential energy into kinetic energy takes place.
(c) You might have seen some beautiful fireworks during Diwali. It is an example of transformation of chemical energy into light energy.
(d) The solar cooker is an application of the heat energy of the sun, while solar cells, solar lamps are applications of the light energy of the sun.
(e) One labourer carried four pans of road metal through a distance of 100 metres. If he carries two pans of road metal through a 200 metre distance equal work will be done.
(f) The capacity that an object has for doing work is called energy.

Page No 83:

Question 2:

Match the pairs.

Group 'A'	Group 'B'
(1) Rolling object	(a) Heat energy
(2) Food	(b) Atomic energy
(3) Stretched bow	(c) Kinetic energy
(4) Sunlight	(d) Potential energy
(5) Uranium	(e) Chemical energy

ANSWER:

Group 'A'	Group 'B'
(1) Rolling object	(c) Kinetic energy
(2) Food	(e) Chemical energy
(3) Stretched bow	(d) Potential energy
(4) Sunlight	(a) Heat energy
(5) Uranium	(b) Atomic energy

Page No 83:

Question 3:

Can you tell ?
(a) When can we say that displacement has taken place?
(b) What should be taken into account for measuring work?
(c) What are the various forms of energy ?
(d) Describe one natural chain of transformation of energy.
(e) Why should we save energy ?
(f) What is ‘green energy’ ?
(g) What are the non-conventional energy resources ?
(h) Which forms of energy from the sun are used in solar energy devices ?
(i) Why should we maximise the use of non-conventional energy resources ?

ANSWER:

(a) We can say that displacement has taken place when the initial and final position of an object is different i.e. there is some distance between the initial and final position of an object.

(b) While measuring work, the magnitude of force applied on an object and the displacement of an object should be taken into account.

(c) Various forms of energy are:

• Mechanical: Kinetic and potential energy are two types of mechanical energy.

• Light

• Heat

• Muscular

• Sound

• Magnetic

• Electrical

• Chemical

• Nuclear

(d) When a candle is lit, the chemical energy stored in its wax gets converted to heat and light energy.

(e) We should save energy because of the following:

• To save money: Wasting energy is same as wasting money. We all know that electricity we use at our homes isn't free but costs us a lot. So, saving energy will save money too. 
• To preserve conventional sources: Most of the energy we use in our daily life is generated using conventional energy resources, such as coal, petroleum, etc. These energy resources are non-renewable in nature. So, if we waste energy, we are indirectly wasting these resources and hence a day will come when these resources will get extinct. So to preserve these non-renewable resources, we should save energy.
• To keep environment clean: Energy saving will help us keep the environment clean. Less energy usage will result in less energy production using coal, petroleum and other conventional sources which pollutes the environment when burnt.

(f) The forms of energy which do not produce smoke and carbon gases such as carbon dioxide or carbon monoxide are known as green energy.

(g) Non-conventional energy resources are inexhaustible in nature and can be used in various forms again and again. For example, wind energy, tidal energy, solar energy, etc. are non-conventional energy resources. 

(h) Heat and light energy of Sun are used in solar energy devices.

(i) Because of increase in population and usage of energy resources, there is a potential danger of limited reserves of conventional energy resources, such as coal, petrol, diesel, crude oil and natural gas, getting exhausted in future. Therefore, it will be better to maximise the use of non-conventional energy resources to remove the danger of extinction of conventional energy resources.

Page No 83:

Question 4:

Who is the odd-one-out ?
(1) Diesel, crude oil, natural gas, wind
(2) A running car, hauling a log, a book kept on a table, picking up the school bag.
(3) Sunlight, wind, waves, petrol
(4) Leaving the fan on in a vacant room, leaving the TV on while working, using AC during winter, putting off the light when going out.

ANSWER:

(1) Wind is the odd one out as it is a non-conventional energy resource. The rest are conventional energy resource.

(2) A book kept on a table is the odd one out as no work is being done in this case. In rest of the cases, work is being done.

(3) Petrol is the odd one out as it is a conventional energy resource. The rest are non-conventional energy resource.

(4) Putting off the light when going out is the odd one out as it is one of the measures of saving energy. The rest involves wastage of energy.

Page No 83:

Question 5:

Find out the types of energy from the following puzzle.

ANSWER:

Force and Types of force.

Question 1:

Choose the term to fill in the blanks.
(a) ...... has to be applied to change the ..... of a ...... object.
(moving, direction, force)
(b) When an elephant drags a wooden log over the land, the forces that are applied on the log are ...... , ....... and ........ .
(muscular force, mechanical force, gravitational force, frictional force)
(c) A ball was set rolling on a large table. If its ...... is to be changed, a ........ will have to be applied on it.
(force, motion, gravitation)
(d) The force of friction always acts ........ the motion.
(along, against)

ANSWER:

(a) Force has to be applied to change the direction of a moving object.
(b) When an elephant drags a wooden log over the land, the forces that are applied on the log are muscular force , gravitational force and frictional force.
(c) A ball was set rolling on a large table. If its motion is to be changed, a force will have to be applied on it.
(d) The force of friction always acts against the motion.

Page No 74:

Question 2:

Match the following :

Group ‘A’	Group ‘B’
(i) An ox pulling a cart	(a) Magnetic force
(ii) Lifting a heavy iron object with a crane	(b) Electrostatic force
(iii) Weighing with a spring balance	(c) Muscular force
(iv) Applying brakes to a bicycle	(d) Gravitational force
(v) Picking up pieces of paper with a plastic scale	(e) Frictional force

ANSWER:

Group ‘A’	Group ‘B’
(i) An ox pulling a cart	(c) Muscular force
(ii) Lifting a heavy iron object with a crane	(a) Magnetic force
(iii) Weighing with a spring balance	(d) Gravitational force
(iv) Applying brakes to a bicycle	(e) Frictional force
(v) Picking up pieces of paper with a plastic scale	(b) Electrostatic force

Page No 74:

Question 3:

One or more forces are acting in the following examples. Name them.
(a) An object falling from a tall building ....
(b) An aeroplane flying in sky ....
(c) Squeezing sugarcane juice with a squeezer ........ .
(d) Winnowing foodgrain ....... .

ANSWER:

(a) An object falling from a tall building: Gravitational force
(b) An aeroplane flying in sky: Mechanical and Gravitational force
(c) Squeezing sugarcane juice with a squeezer: Muscular force
(d) Winnowing foodgrain: Muscular and Gravitational force

Page No 75:

Question 4:

Explain in your own words giving one example each.
Muscular force, gravitational force, mechanical force, electrostatic force, the force of friction and magnetic force.

ANSWER:

Muscular force: The force applied by the action of muscles in our body is termed as a muscular force. For example, when you pick up a book placed on the table using your hands, you apply muscular force.

Gravitational force: It is the force that is exerted by the Earth on every object, which is near or on its surface. For example, an apple falling from a tree branch towards the ground is due to gravitational force.

Mechanical force: The force generated by the means of a machine is known as mechanical force. For example, when a car gets started, its engine creates a mechanical force on the tyres that help the car to accelerate. So here, the movement of car occurs due to the force generated by the machine on the tyres.

Electrostatic force: Electrostatic force is the force that exists either between the two charged bodies, or between a charged and an uncharged body. For example, the charged scale attracts the pieces of paper by a non-contact force known as electrostatic force.

The force of friction: The force which acts opposite to the direction of motion of a body is known as the force of friction. For example, a ball rolling on a ground stops after sometime because of frictional force acting between the ground and the ball.

Magnetic force: The force exerted by a magnet is known as magnetic force. For example, separation of iron stuffs from junk is done with the help of magnetic force.

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Question 5:

Why ?
(a) Machines are oiled from time to time.
(b) An object thrown upwards comes down after reaching a point.
(c) Powder is sprinkled on a carrom board.
(d) The ramp at a railway station has a rough surface.

ANSWER:

(a) A machine is oiled from time to time to reduce friction between its body parts. By doing so, life span of a machine increases.

(b) An object thrown upwards comes down after reaching a point. This is because of the Earth's gravitational pull.

(c) Powder is sprinkled on a carom board to reduce friction between the striker/carom coins and the carom board. The powder smoothens the surface of the board and thus the striker and coins can move on it easily.

(d) The ramp at a railway station has a rough surface so that the friction between our feet and the ground is enough for us to walk comfortably and without tripping.

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Question 6:

In what way are we different?
(a) Muscular force and mechanical force.
(b) The force of friction and gravitational force.

ANSWER:

(a) 

Muscular force	Mechanical force
The force applied by the action of muscles in our body is termed as a muscular force.	The force generated by the means of a machine is known as mechanical force.
For example, when you pick up a book placed on the table using your hands, you apply muscular force.	For example, when a car gets started, its engine creates a mechanical force on the tyres that help the car to accelerate. So here, the movement of car occurs due to the force generated by the machine on the tyres.

(b) 

The force of friction	Gravitational force
The force which acts opposite to the direction of motion of a body is known as the force of friction.	It is the force that is exerted by the earth on every object, which is near or on its surface.
It is a contact type of force.	It is non-contact type of force.
For example, a ball rolling on a ground stops after sometime because of frictional force acting between the ground and the ball.	For example, an apple falling from a tree branch towards the ground is due to gravitational force.

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Question 7:

Write answers to the following questions in your own words.
(a) What are the things that can be done by applying force?
(b) What is meant by weight?
(c) Which machines run on muscular force?

ANSWER:

(a) Following things can be done by applying force:

(i) It can move a body initially at rest.

(ii) It can bring a moving body to rest.

(iii) It can change the direction of a moving body.

(iv) It can change the speed of a moving body.

(v) It can change the shape of a body.

(vi) It can change the size of a body.

(b) Weight is the force exerted on a body due to the gravitational pull of Earth.

(c) Machines which run on muscular force are:

• Bicycle
• Rickshaw
• Hand pump
• Stitching machine
• Hand cart

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Question 8:

Solve the following crossword puzzle.

Down :
(1) ....... force is to be applied to push a scooter that has failed.
(2) ........... force can be used to pick up scattered pins.
Across :
(1) A .......... pulls an iron nail towards itself.
(3) .......... force was used when the farm was ploughed with a tractor.
(4) It is due to the force of ............ that raindrops fall to the ground

ANSWER:

Nutrition and Diet

Question 1:

Fill in the blanks.
(a) The process of intake of food and utilising it for all life processes is called .......... .
(b) All the substances in our food which are useful for various bodily processes are called .......... .
(c) Carbohydrates and .......... provide .......... to our body.
(d) In a balanced diet, all the nutrients are present in the ....... proportion.
(e) In the food pyramid, cereals are given the maximum space because they fulfil our .......... requirement.
(f) Intake of more food than necessary causes .......... .

ANSWER:

(a) The process of intake of food and utilising it for all life processes is called nutrition.
(b) All the substances in our food which are useful for various bodily processes are called nutrients.
(c) Carbohydrates and fats provide energy to our body.
(d) In a balanced diet, all the nutrients are present in the right proportion.
(e) In the food pyramid, cereals are given the maximum space because they fulfil our nutritional requirement.
(f) Intake of more food than necessary causes overnutrition.

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Question 2:

Spot the following in the table of vitamins and minerals.
(a) The nutrient present in citrous fruits.
(b) Vitamins / minerals present in milk.
(c) Causes and symptoms of night blindness, scurvy, rickets, beriberi.
(d) Foods required to prevent the above diseases.
(e) Causes of anaemia.
(f) Essential mineral for healthy bones and teeth.
(g) Sensory organ affected due to the deficiency of Vitamin A

ANSWER:

(a) The nutrient present in citrous fruits- Vitamin C
(b) Vitamins / minerals present in milk- Vitamin B₁₂ and Vitamin D.
(c) Causes and symptoms of night blindness, scurvy, rickets, beriberi
 

Disease	Causes	Symptoms
Night blindness	Deficiency of Vitamin A	Inability to see in dim light
Scurvy	Deficiency of Vitamin C	Bleeding of gums
Rickets	Deficiency of Vitamin D	Softening of pones causing pain and fractures
Beri beri	Deficiency of Vitamin B1	Nerve disorders

(d) Foods required to prevent the above diseases.
 

Disease	Foods to avoid these diseases
Night blindness	Carrot, milk, butter, dark green vegetables, sweet potato
Scurvy	Amla, kiwi, oranges, other citrus fruits, tomato, green leafy vegetables
Rickets	Milk, fish, eggs and butter
Beri beri	Milk, fish, meat, cereals, nuts, pulses

(e) Causes of anaemia- defeciency of iron can result in anaemia as it is required for the formation of red blood cells.
(f) Essential mineral for healthy bones and teeth- Vitamin D
(g) Sensory organ affected due to the deficiency of Vitamin A- Eyes

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Question 3:

Choose the correct alternative.

(a) Pulses are a very good source of .......... .

(1) carbohydrates	(2) proteins
(3) fats	(4) minerals

(b) .......... provide maximum energy to the body.

(1) Cereals	(2) Leafy vegetables
(3) Water	(4) Amla

(c) Goitre is caused by a deficiency of the mineral .......... .

(1) iron	(2) calcium
(3) iodine	(4) potassium

(d) .......... is a type of junk food.

(1) Orange	(2) Milk
(3) Bhakri	(4) Chocolate

ANSWER:

(a) Pulses are a very good source of proteins.
(b)Cereals provide maximum energy to the body.
(c) Goitre is caused by a deficiency of the mineral iodine.
(d) Chocolate is a type of junk food.

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Question 4:

Use the food pyramid to select food items of your choice for three days.
Conditions :
(1) The diet for all three days should be balanced.
(2) There should be variety in the items chosen for the three days.

ANSWER:

Day 1-
Cereal like cornflakes and milk, apple, roti, sabzi and dal

Day 2
Bread and butter with milk, rice/ roti and chicken, curd, any one type of fruit, salad

Day 3
Poha, green vegetable and dal with rice or roti, raita, one fruit, vegetable sandwich.

Substances in Daily Use

Substances in Daily Use

Question 1:

Fill in the blanks using proper words.
(a) Rubber made by vulcanization is a ...... material.
(b) Man-made materials are made by .......... natural materials.
(c) ............. thread was developed simultaneously in New York and London.
(d) Rayon is also known as ............

ANSWER:

(a) Rubber made by vulcanization is a man-made material.
(b) Man-made materials are made by processing natural materials.
(c) Nylon thread was developed simultaneously in New York and London.
(d) Rayon is also known as synthetic silk.

Question 2:

Answer the following questions.

ANSWER:

(a) Why did the need for man-made materials arise?

a. For several years, humans have been dependant on natural materials to meet their demands. However, there has been a shift towards the use of man made materials as well. Increasing population, deforestation and limited natural resources are some of the reasons due to which the need for man made materials arised. Another reason which led to the increase in the use of man made material was to get a comfortable lifestyle.

(b) Which are the natural materials obtained from plants and animals?

b. 

Sources	Natural material	Objects
Plants	Wood	Furniture
	Rubber	Ballon, tyres etc.
	Cotton	Clothes
Animals	Fur	Hats, Sweaters
	Leather	Handbags, shoes
	Silk	Sarees

(c) What is vulcanization?
c. Vulcanization is the process carried out for the production of rubber. In this process, raw rubber is heated with a mixture of sulphur and an appropriate additive, at a temperature range of 61.85${\mathrm{<merror><mtext>Unknown\; node\; type:\; sup</mtext></merror>}}^{}$ C to 141.85⁰C for three to four hours. Sulphur is added to give toughness to rubber.

(d) Which natural materials are used to obtain fibres?

d. Natural materials obtained from plants and animals are used to obtain fibers. For example, wool and silk are natural materials of animal origin which are used for obtaining fibers. Wool is obtained from the fleece (hair) of sheep or yak and silk is obtained from the cocoons of a silk moth. Cotton and jute are examples of natural materials of plant origin which are used for obtaining fibers.

Question 3:

What are we used for ?
(a) Soil
(b) Wood
(c) Nylon
(d) Paper
(e) Rubber

ANSWER:

a. Soil- It is used in construction, pottery, medicine and cosmetics.
b. Wood- It is used in making furnitures, as a source of fuel, utensils, hand tools, musical instruments, wooden toys etc.
c. Nylon- It is used in making canopies of parachutes, tents, sleeping bags, sails, rope, tennis strings, fishing poles and lines, cookware etc.
d. Paper- It is used in making bags, envelopes, notebooks, packaging purpose etc.
e. Rubber- Balloons, erasers, rubber toys, rubber balls etc.

Question 4:

How is paper manufactured? Write in your own words.

ANSWER:

Paper is manufactured by the following process:

• Logs of wood are made to pass through a debarker, where the barks of the tree are separated.
• Then the wood is chopped into small pieces and is mixed with some chemicals and water in digetser for the formation of the pulp.
• The obtained pulp is washed refined and sometimes even bleached.
• The pulp is made to travel down the screen to remove excess of water and then to the rollers where it is being dried and squeezed between large rollers to form rolls of paper. 

Question 5:

Give scientific reasons.

ANSWER:

(a) We must use cotton clothes in summer.

a. We must use cotton clothes in summers because they protect us from the heat of the sun. They absorb sweat and help keep our bodies cool. The pores in cotton clothes allow the free movement of air, which helps cool our bodies.

(b) We must observe economy in the use of materials.
b. We must observe economy in the use of materials because they directly or indirectly affect our environment. Most of the natural materials which we obtain from our environment are exhaustible/non renewable resources i.e. once these resources are finished they cannot be renewed again or even if they can, it would take several years to do so. For example, our forests from where we obtain wood are precious resources because once a forest is destroyed, it would take several years to renew that forest. Also, destroying the forests for our needs affects the habitat of several other species of organisms and plants. The man made materials which we use are largely non biodegradable for example plastic etc. Increased use of man made materials pose a threat to the environment because their disposal is not easy and leads to environmental pollution. These examples state the importance of judicious use of both natural and man made materials.

(c) Saving paper is the need of the hour.

c. We very well know that paper is obtained from trees. Trees are important resources because they not only provide us with wood or paper but are also a habitat for various organisms. They are important in maintaining the climate as well. The more paper we use or waste, the more no. of trees will have to be cut down for this purpose, thus leading to v arious kinds of harmful effects on our environment. We should make a genuine effort in saving paper by adopting small steps which can make a huge difference.

(d) Man-made materials have more demand.

d. Man made materials have more demand because of their characteristics like easy to use, low cost of production, cheaper products and variety of things which can be made from them.

(e) Humus is a natural material.

e. Humus is a natural material because its formation is a natural process. It is the dark-coloured layer of top soil that is rich in nutrients. The decomposers convert the dead plants and animals into humus that is utilised by the plants. It increases the fertility of the soil.

Question 6:

Find out.
(1) How is lac obtained from nature?

ANSWER:

a. Lac is a natural resin and is a product of animal origin. It is secreted by an insect, known as lac-insect. In order to obtain lac, these insects are cultured and the technique is called lac-culture. Lac culture requires proper care of host plants, regular pruning of host plants, propagation, collection and processing of lac. The lac insect lives as a parasite, feeding on the sap of certain trees and shrubs. Lac secretion begins as soon as the larva of the insect settles on the plant. Intially, lac has a shining appearance but later on it turns harder on coming in contact wih air.
This lac is then collected and used for making jewellery etc.


(2) How are pearls obtained?
b. Pearls are precious jewels and the only gems created by a living animal. They are formed when a microscopic foreign object finds its way inside a mussel or oyster.

The animal coats the object with a substance called nacre. With time, several layers of nacre build up over the foreign material thus leading to the formation of a pearl. These oyesters/mussels are collectd from the sea and opened to collect these pearls.