Disaster Management

Question 1:

What are the emergency contact numbers of the following?
(a) Police Control Room
(b) Fire brigade
(c) Ambulance
(d) National level single emergency number for disaster relief.

ANSWER:

(a) 100 should be dialled for Police control room.
(b) 101 should be dialled for Fire brigade.
(c) 102 should be dialled for Ambulance.
(d) 108 should be dialled for National level single emergency number for disaster relief.

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Question 2:

What first aid will you provide in the following situations?
(a) Dog bite
(b) Scratches/ bleeding
(c) Burns/scalds
(d) Snakebite
(e) Sunstroke

ANSWER:

(a) Following first aid should be provided for dog bite:

• A dog bite wound must be very thoroughly cleaned, first with soapy water and then with an antiseptic.

• If this is not done, the bite might lead to rabies.

• Cover the wound with a bandage.

• See a doctor immediately.

(b) Following first aid should be provided for scratches/bleeding:

• Clean the wound with cotton soaked in antiseptic lotion.

• Apply bandage (in case of a smaller wound) or antiseptic lotion and wrap with a bandage (in case of a bigger wound).

• In case of heavy bleeding, tie a handkerchief above the wound to stop bleeding.

​(c) Following first aid should be provided for burns/scalds:

Minor Burns:

• Pour plenty of cold water immediately over it.

• Apply an anti-burn ointment.

• Immediate home remedies:

  •  Apply baking soda mixed with water

  • Apply the paste of turmeric and milk

  • Apply the paste of raw potato

Severe Burns:

• In case clothes of a person catch fire, cover the person with a blanket and make the person roll over the ground in order to put out the fire.

• Make the person lie down in an open space.

• Remove the burnt clothes that are not sticking to the body.

• Give him plenty of water to drink.

• Apply anti-burn ointment on the burn.

​(d) Following first aid should be provided for snakebite:

• Keep the person calm and restrict any movement.

• Do not make him eat or drink anything.

• Tightly tie a handkerchief above the bite to prevent the poison from spreading and reaching the heart or the nervous system.

• Seek medical attention immediately.

​(e) Following first aid should be provided for sunstroke:

• Make the person sit in the shade or a cool place.

• Cover the body with cool damp sheets.

• Make the person drink plenty of water or liquids.

• Apply cooling measures like ice towels.

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Question 3:

Write the causes of the following :
(a) Floods
(b) Forest fires
(c) Land slides/building collapse
(d) Storms
(e) Earthquakes

ANSWER:

(a) Following can be the cause of floods in a region:

• It may occur due to heavy rainfall that leads to overflow of water from the water bodies.
• Sudden melting of huge amount of ice at mountain tops can lead to flood in the regions nearby to mountains.
• Cloudburst can lead to flood.

​(b) Following can be the cause of forest fires:

• Natural calamities like lightning strikes falling on the trees of a forest.
• Man made activities like smoking, setting thermal factories or campfires near the forest area, etc.

(c) Landslide/building collapse can occur due to following reasons:

• Earthquake can cause landslide and building collapse.
• Volcanic eruption can cause landslide.
• Usage of poor quality material for construction of building can lead to its collapse.
• Mining and weathering can cause landslides.

(d) Storms can occur either naturally or due to ecological imbalance occuring due to various human activities.
 
(e)  Earthquakes can occur due to following reasons:

• Volcanic eruption

• Meteors falling on the Earth’s surface

• Underground explosions. For example, underground nuclear tests.

• Collapsing structures such as mines etc.
   
• ​Mining and construction of big dams.

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Question 4:

Answer the following questions.
(a) What is meant by ‘disasters’?
(b) What are the types of disasters?
(c) What is meant by ‘disaster management’?
(d) Which are the main components of disaster management?

ANSWER:

(a) A sudden happening that causes enormous damage to life, property and social aspects of a nation or society is called a disaster.

(b) Disasters are of two types:
Man-made disasters: These disasters are the result of technological or human hazards. Examples of man-made disasters are road accidents, forest fires, collapsing of building due to usage of poor quality materials, etc.
Natural disasters: There are due to imbalance occurring in nature various environmental factors. Examples of natural disasters are earthquakes, volcanic eruption, etc.

(c) Disaster management is the strategy and course of action to be executed at the time of any disaster to save as much life as possible. 

(d) Main components of disaster management are:
Preparation: A plan is created to minimise the damage if a disaster occurs.
Redemption: It is the plan to minimise the damage to the society and country.
Preparedness: A plan is chalked out to get quick response from public and administration.
Impact of disaster: Intensity of disaster and disaster management are reviewed.
Response: This stage deals with providing immediate response after an incident has occurred.
Resurgence: It is an important link between emergency measures and national progress. It includes the steps which are required for the welfare and rehabilitation of the nation. 
Restoration: It is an important link between measures after disaster and national development. It includes steps useful for progress of
nation and rehabilitation.

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Question 5:

Find out about the work of a ‘Sarpa-mitra’.

ANSWER:

Sarpamitra (friend of snake) protects and safeguards snakes. They also demonstrate to people the various aspects of snakes and snake bites, what precautions and first-aid should be given in case of snake bite and the general idea of how to classify the snakes into poisonous and non-poisonous.

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Question 6:

Find out what a first aid kit/box contains.

ANSWER:

First aid box should contain the following things:

• First-aid manual
• Sterile gauze pads of different sizes
• Adhesive tape
• Adhesive bandages in several sizes
• Elastic bandage
• A splint
• Antiseptic wipes
• Soap
• Antibiotic ointment
• Antiseptic solution (like hydrogen peroxide)
• Hydrocortisone cream (1%)
• Extra prescription medications
• Tweezers
• Sharp scissors
• Safety pins
• Disposable instant cold packs
• Calamine lotion
• Alcohol wipes or ethyl alcohol
• Thermometer
• Tooth preservation kit
• Plastic non-latex gloves (at least 2 pairs)
• Flashlight and extra batteries
• A blanket
• Mouthpiece for administering CPR (can be obtained from your local Red Cross)
• List of emergency phone numbers

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Question 7:

Suggest remedial measures for dealing with natural or man-made disasters.

Disaster	Remedy	Disaster	Remedy
Fire		Earthquake
Building collapse		Deluge
Road accident		Storm
Flood		Tsunami
War		Drought
Bomb explosion		Landslide

ANSWER:

Disaster	Remedy	Disaster	Remedy
Fire	Call fire brigade, use fire extinguisher	Earthquake	Give help to clear debris, call ambulance to send victims to hospitals
Building collapse	Give help to clear debris, call ambulance to send victims to hospitals	Deluge	Donate food and clothing for flood victims, stay at some height if possible
Road accident	Call ambulance, give immediate first-aid and emotional support	Storm	Provide shelter and help in clearing the debris
Flood	Donate food and clothing for flood victims, stay at some height if possible	Tsunami	Move to a safer place, donate food and clothing for victims
War	Give shelter to innocent victims, provide food and clothing and first-aid to the victims	Drought	Donate food and water for victims, provide shelter and monetary help
Bomb explosion	Call ambulance, take the victims to a safer place and provide basic first-aid	Landslide	Help in rehabilitation services

Ch.2 The Living World

Question 1:

Write the answers to the following questions in your own words.
(a) What are the differences between plants and animals ?
(b) What are the similarities between plants and animals ?
(c) How is the plant kingdom useful to us ?
(d) How is the animal kingdom useful to us ?
(e) What makes living things different from non-living things ?

ANSWER:

a. 

Plants	Animals
They can make their own food by the process of photosynthesis. They are autotrophs.	They cannot make their own food. They are heterotrophs.
They show movement, but cannot show locomotion i.e., they cannot change their position from one place to another.	They show movement as well as locomotion.
They show response to stimuli, but lack sense organs.	They also show response to stimuli and have well-developed sense organs.
They grow throughout their life.	They stop growing once they reach their adult form.

b. Apart from various differences, plants and animals also have some similarities. Plants and animals both show vital processes like growth, reproduction, respiration and excretion. Both of them require energy to carry out their various functions.


c. The plant kingdom has various uses in our life like:

• they provide habitat for a variety of organisms.
• they are the major producers of oxygen.
• they provide us with wood, that is a source of fuel and other products.
• they provide us with plants that have medicinal and ornamental importance.

d. The animal kingdoms is useful to us in various ways. The animals from the animal kingdom can be domesticated for various purposes. There are three categories of useful domesticated animals.

• Milk and Flesh Yielding Animals- These are the animals from which we obtain food products. They include cattle, goat, poultry, pig, sheep, etc.

• Draught Animals- These are the animals used for transportation, ploughing of fields, and other agricultural activities. They are hardy and can lift heavy loads.

• Fibre, Hide, and Skin Yielding Animals- These animals yield useful products such as fibre (wool), hide, etc. They include sheep, goat, cattle, camel, etc.

e. 

Living things	Non-living things
They are made up of cells.	They are not made up of cells.
They show movement, but the energy for movement comes from within the organism.	They show movement by taking external force or energy.
They require food.	They do not require food.
Growth in them is irreversible.	Growth is reversible.
Respiration occurs in which food is oxidised to release energy.	They do not require respiration.
Reproduction occurs in living things.	Non-living things do not reproduce.

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Question 2:

What helps them to breathe ?

(a) A fish	(b) A snake
(c) A crane	(d) An earthworm
(e) Man	(f) A banyan tree
(g) A caterpillar

ANSWER:

(a) A fish- Gills
(b) A snake- External nares (they are similar to nose in humans)
(c) A crane- Nostrils
(d) An earthworm- Skin
(e) Man- Nose
(f) A banyan tree- Microscopic pores on leaves
(g) A caterpillar- Tiny holes on their body known as spiracles

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Question 3:

Fill in the blanks with the proper words from the brackets.
(a) The process by which plants make their own food is called ............ .
(b) To inhale ......... and to exhale ........ is called respiration.
(c) The elimination of waste substances from the body is called ............ .
(d) The ability to respond to an event is called ..... to ...... .
(e) On completing their lifespan, every living thing ........ .
(oxygen, dies, excretion, carbon dioxide, responsiveness, photosynthesis, stimuli)

ANSWER:

(a) The process by which plants make their own food is called photosynthesis.
(b) To inhale oxygen and to exhale carbon dioxide is called respiration.
(c) The elimination of waste substances from the body is called excretion.
(d) The ability to respond to an event is called responsiveness to stimuli.
(e) On completing their lifespan, every living thing dies.
(oxygen, dies, excretion, carbon dioxide, responsiveness, photosynthesis, stimuli)

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Question 4:

Write the uses of these animals and plants.
Animals : Honeybees, sharks, yaks, sheep, earthworms, dogs, bivalves, horses, mice.
Plants : Ginger, mango, eucalyptus, babul (acacia), teak, spinach, aloevera, turmeric, holy basil, karanja , moh , mulberry, grapevine.

ANSWER:

Animals	Uses
1. Honeybees	Provide us with honey and wax.
2. Sharks	Used in medicines, cosmetics, pet products etc.
3. Yaks	Used for obtaining wool.
4. Sheep	Used for obtaining wool.
5. Earthworm	Used in agriculture for composting(vermicomposting).
6. Dogs	As pets.
7. Bivalves	Used as a source of food.
8. Horses	For transportation.
9. Mice	As pets and models for testing various experiments.

Plant	Uses
1. Ginger	Used in foods and for medicinal purposes.
2. Mango	For obtaining fruits.
3. Eucalyptus	For making paper and essential oils.
4. Babul (Acacia)	Used in tooth pastes and other medicinal purposes.
5. Teak	Used in making furnitures.
6. Spinach	Used as food.
7. Aloe vera	Used for cosmetic and medicinal purposes.
8. Turmeric	Used as a spice and for various medicinal purposes.
9. Holy basil	Spiritual importance and for various medicinal purposes.
10. Karanja	Used for medicinal purposes like treating skin diseases.
11. Moh	Used for medicinal purposes.
12. Mulberry	For obtaining fruits.
13. Grapevine	For obtaining fruits and making wine.

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Question 5:

What are the peculiarities of the movements of these living things ?
Living things : Snakes, tortoises, kangaroos, eagles, chameleons, frogs, gulmohur, sweet potato creeper, dolphins, ants, rattlesnakes, grasshoppers, earthworms.

ANSWER:

Living thing	Movement
1. Snakes	Crawl
2. Tortoises	Swim and crawl
3. Kangaroos	Jump
4. Eagles	Fly
5. Chameleons	Walk
6. Frogs	Swim and hop
7. Gulmohar	Grows in the direction of light
8. Sweet potato	Grows in the direction of gravity
9. Creeper	Grows in the direction of light
10. Dolphins	Swim using fins
11. Ants	Walk
12. Rattlesnakes	Crawl
13. Grasshoppers	Hops
14. Earthworm	Crawl

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Question 6:

Write in detail about how the plants and animals found in your surroundings prove useful or harmful.

ANSWER:

There are so many kinds of plants and animals which we find in our surroundings. These plants and animals can be both useful and harmful to us. The follwoing points support this fact:

Useful plants:

• Plants like tulsi, mint, ashwagandha, neem etc. are called medicinal plants and have various medicinal properties.
• There are many plants which provide us with fruits and vegetables like mango etc.
• Certain plants are used for ornamental purposes like money plant etc.
• There are plants from which we obtain rubber which is used in the manufacture of tiers, tubes, raincoats, belts, sports goods, etc.
• Flowers like rose, jasmine, lavender, champa, saffron etc. are used for extracting sweet smelling oils called perfumes.

Harmful plants:

• Partehnium is a type of plant which can cause pollen allergy to humans.
• White Cedar is a small neem-like tree with attractive yellow fruits. These are lethal if taken by children and cause vomiting, diarrhea and difficulty in breathing in adults.
• Leaves of colocasia and pods of nettle cause itching.
• Datura is an example of poisnous plants.

Useful animals

• Milk and Flesh Yielding Animals- These are the animals from which we obtain food products. They include cattle, goat, poultry, pig, sheep, etc.
• Draught Animals- These are the animals used for transportation, ploughing of fields, and other agricultural activities. They are hardy and can lift heavy loads.
• Fibre, Hide, and Skin Yielding Animals- These animals yield useful products such as fibre (wool), hide, etc. They include sheep, goat, cattle, camel, etc.

All animals and insects are not useful, some of them can cause a lot of harm to our health and also to our crops. Such animals and insects are known as pests.

• Insects, like grasshoppers, beetles etc. cause enormous damage to the agricultural crops and thus affect their yield.
• Animals like tigers, lions etc. can enter human settlement and may kill domestic animals and people.
• Caterpillars or larvae of many insects feed on the leaves on which they live.
• Stored grains are also attacked by rodents like rats and rabbits and by many kind of moths, caterpillars and beetles.
   

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

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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.

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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

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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

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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.

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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.

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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

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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.

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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

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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.

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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

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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.

Page No 75:

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: