Category: Science

NCERT Solutions for Class 6 Science Chapter 14 Water

Topics and Sub Topics in Class 6 Science Chapter 14 Water:

Section Name	Topic Name
14	Water
14.1	How much water do we use?
14.2	Where do we get water from?
14.3	Water cycle
14.4	Back to the oceans
14.5	What if it rains heavily?
14.6	What happens w it does not rain for a long period?
14.7	How can we conserve water?
14.8	Rainwater harvesting
14.9	Summary

 1. Fill up the blanks in the following:
(a) The process of changing of water into its vapour is called_______________ .
(b) The process of changing water vapour into water is called_____________ .
(c) No rainfall for a year or more may lead to _____________ in that region.
(d) Excessive rains may cause__________ .
Ans:
(a) evaporation or vaporisation
(b) condensation
(c) droughts
(d) flood

2. State for each of the following whether it is due to evaporation or condensation:
(a) Water drops appear on the outer surface of a glass containing cold water.
(b) Steam rising from wet clothes while they are ironed.
(c) Fog appearing on a cold winter morning.
(d) Blackboard dries up after wiping it.
(e) Steam rising from a hot girdle when water is sprinkled on it.
Ans: 
(a) condensation
(b) evaporation
(c) condensation
(d) evaporation
(e) evaporation.

3. Which of the following statements are “true”?
(a) Water vapour is present in air only during the monsoon.
(b) Water evaporates into air from oceans, rivers and lakes but not from the soil.
(c) The process of water changing into its vapour is called evaporation.
(d) The evaporation of water takes place only in sunlight.
(e) Water vapour condenses to form tiny droplets of water in the upper layers of air where it is cooler.
Ans: 
(a) False
(b) False
(c) True
(d) False
(e) True.

4. Suppose you want to dry your school uniform quickly. Would spreading it near an anghiti or heater help you? If yes, how?
Ans: Yes, to dry the school uniform quickly, the uniform is spread near an anghiti or heater because evaporation is rapid at higher temperature. Higher the temperature faster is the rate of evaporation. So the uniform is dried up quickly.

5. Take out a cooled bottle of water from refrigerator and keep it on a table. After some time you notice a puddle of water around it. Why?
Ans: The cooled water bottle has very cold exposed surface. Due to cool surface there is condensation of water-vapour from air on the surface of water bottle because water vapour is present in atmosphere. The condensed water molecules spread around the bottle. So a puddle of water is noticed after sometime.

6.To clean their spectacles, people often breathe out on glasses to make them wet. Explain why the glasses become wet?
Ans: The breathe out gases contain water-vapour. The water-vapour condenses at spectacles so glass becomes wet and with the help of small amount of water, it is easy to clean the spectacles.

7. How are clouds formed?
Ans: The water present on the earth evaporates due to heating by the sun. The water vapour in the air condenses to form tiny droplets of water at high altitude, which appears as clouds. Thus clouds are formed by the condensation of water vapours present in air at high altitude.

8. When does a drought occur?
Ans: If there is no rain for a long period or for many years then there is scarcity of water in that region. This leads to drought.

Class 6 Science Chapter 14 VERY SHORT ANSWER TYPE QUESTIONS

1. Write the sources of water on the earth.
Ans:  Sources of water on the earth are:
Seas, Oceans, Rivers, Springs, Tubewells, etc.

2. In which forms, water exists on the earth?
Ans: Water exists on the earth in all three physical forms: ice, water and water vapour.

3. What is transpiration?
Ans: Loss of water in the form of water vapour through stomata of leaves is called transpiration.

4. How are the clouds formed?
Ans: Clouds are formed by the condensation of water vapour at high altitude.

5. What is meant by the conservation of water?
Ans: Careful, economical and wise use of water and avoiding the wastage of water is called conservation of water.

Class 6 Science Chapter 14 SHORT ANSWER TYPE QUESTIONS

1. Mention two main functions of water for living organisms.
Ans: Two main functions of water for living organisms are:
1. Water is essential for the germination of seeds, growth of plants and in photosynthesis.
2. Water is used for the transportation of people and goods.

2. Why is ocean water not suitable for domestic use?
Ans: Sea and ocean water contains large amounts of various salts. It is due to these salts the ocean water is salty and cannot be used for drinking, washing and for irrigation purposes.

3. Why does the water split on the floor disappear after some time?
Ans:  Due to evaporation the water split is changed into water vapour. So it disappears after some time.

4. How does heavy rain affect us?
Ans: Heavy rains may cause:
1. A rise of water level in dams, rivers, lakes, etc.
2. Waterlogging and floods.
3. Floods cause damage to property, crops and animals.

5. How does the failure of rainfall affect people on the earth?
Ans: The failure of rainfall can cause the following:
1.The soil becomes dry.
2. Water level in rivers, lakes, dams, etc. may fall. Ponds and canals may even dry up.
3. The ground water level falls.

6. Name two processes responsible for the formation of clouds.
Ans:  Evaporation and transpiration.

There are 4 containers A, B, C and D with same amount of water in each. Answer the following based on them.
(a) Name the container in which water will evaporate faster than all others.
(b) Name the container in which water will evaporate very slowly.
Give reason for your answer.
Ans.
(a) C – More is the exposed surface area, more will be evaporation of water.
(b) B – As it is closed, no evaporation takes place.

8. During winters why do we see more fog in close areas where there are lots of .trees?
Ans:  Due to lots of trees, air at that place contains much more water vapour during winters. These vapour condense on dust or smoke particles forming thick fog.

Class 6 Science Chapter 14 LONG ANSWER TYPE QUESTIONS

1. What is meant by conservation of water? Suggest three methods to conserve water.
Ans:  Careful and economical use of water and avoiding its wastage is called conservation of water.
Suggestions for conserving water:

1. Use only the required quantity of water.
2. Trees and forests help in causing rainfall. So to conserve water, we should plant more and more trees.
3. By collecting rainwater in tanks, ponds or by constructing check dams.

2. What is rainwater harvesting? Describe the method of rainwater harvesting.
Ans: Rainwater harvesting is the collection of rainwater and storing for future use. In this system rainwater in collected from the rooftops by means of pipes into storage tank for later use.
Methods of Rainwater Harvesting:

1. Rooftop rainwater harvesting. In this system, the rainwater from the rooftop is collected in a storage tank, through pipes.
2. Another method, a big pit is dug near house for collecting rainwater. This pit is filled with different layers of bricks, coarse gravels and sand or granite pieces.

NCERT Solutions

NCERT Solutions for Class 6 Science Chapter 13 Fun with Magnets

Topics and Sub Topics in Class 6 Science Chapter 13 Fun with Magnets:

Section Name	Topic Name
13	Fun with Magnets
13.1	Magnetic and non-magnetic materials
13.2	Poles of magnet
13.3	Finding directions
13.4	Make your own magnet
13.5	Attraction and repulsion between magnets

1. Fill in the blanks in the following:
(i) Artificial magnets are made in different shapes such as_________ ,_______ and
(ii) The materials which are attracted towards a magnet are called_________
(iii) Paper is not a________
(iv) In olden days, sailors used to find direction by suspending a piece of
(v) A magnet always has ________poles.
Ans:
(i) bar magnet, horse-shoe magnet and cylindrical magnet
(ii) magnetic materials
(iii) magnetic
(iv) bar magnet or lode stone
(v) two or a pair of

2. State whether the following statements are true or false:
(i) A cylindrical magnet has only one pole.
(ii) Natural magnets were discovered in Greece.
(iii) Similar poles of a magnet repel each other.
(iv) Maximum iron filings stick in the middle of a bar magnet when it is brought near them.
(v) Bar magnets always point towards North-South direction when suspended freely in air.
(vi) A compass can be used to find East-West direction at any place.
(vii) Rubber is a magnetic material.
Ans: 
(i) False
(ii) True
(iii) True
(iv) False
(v) True
(vi) True
(vii) False

3. It was observed that a pencil sharpener gets attracted by both the poles of a magnet although its body is made of plastic. Name a material that might have been used to make some part of it.
Ans:  Iron is used to make some part of sharpener due to which it is attracted toward magnet.

4.  Column I shows different positions in which one pole of a magnet is placed near that of the other. Column II indicates the resulting action between them for each situation. Fill in the blanks.

Ans:

5. Write any two properties of a magnet.
Ans:  Two properties of magnets are:
(i) A magnet has two poles: North pole and South pole.
(ii) Like poles repel each other and unlike poles attract each other.

6. Where are poles of a bar magnet located?
Ans: Poles are located at the ends of bar magnet just before the ends. These are north and south poles.

7. A bar magnet has no markings to indicate its poles. How would you find out near which end is its north pole located?
Ans: Take the bar magnet and suspend it freely with the help of a thread, the end that points towards north pole will be regarded as north end of the magnet. Take a bar magnet with known/marked poles on it. Let the north pole of the magnet be brought closer to the suspended magnet at the end that is pointing towards north, if it shows repulsion than it is confirmed.

8. You are given iron strip. How will you make it into a magnet?
Ans:  Making a magnet: Take an iron strip and place it on the table. Now take a bar magnet and place one of its poles near one edge of the strip of iron. Without lifting it move it along the length of the iron strip till you reach the other end. Now lift the magnet and bring the pole to the same point of strip from where yob began. Repeat this process about 30-40 times. Bring some iron fillings near the strip and observe that the strip attracts the fillings. This indicates that the iron strip becomes magnet.
Remember that the pole of magnet and direction of its movement should not change.

9. How is compass used to find direction?
Ans: A compass is a small case of glass. A magnetised needle is pivoted inside the box. The needle can rotate freely. Compass also has a dial with directions marked on it. The compass is kept at the place where we want to know the directions. When the needle comes to rest it indicates north-south direction. The compass is then rotated until the north and south marked on the dial are at the two ends of the needle. Usually different colours are used to point the ends of needle to identify the north and the south poles.

10. A magnet was brought from different directions towards a toy boat that has been floating in water in a tub. Effect observed in each case is stated in Column I. Possible reason for the observed effects are mentioned in Column II. Match the statements given in Column I with those in Column II. 

Ans:

Class 6 Science Chapter 13 VERY SHORT ANSWER TYPE QUESTIONS

1. Name the compound of iron contained in lode stone.
Ans: The compound of iron is iron oxide or magnetite.

2. Name the shepherd after which magnet was named.
Ans: Magnets.

3. How can you separate a magnetic substance from a mixture?
Ans: By using a bar magnet, the magnetic substance is separated from mixture.

4. At which place on a magnet, its magnetic force is maximum?
Ans: At poles.

5. In which direction does a suspended magnet come to rest?
Ans: Magnet comes to rest in N-S (north-south) direction.

6. What happens when N-pole of a magnet is brought near the N-pole of a suspended magnet?
Ans: There is repulsion between these two magnets as there is repulsion between like poles.

Class 6 Science Chapter 13 SHORT ANSWER TYPE QUESTIONS

1. Draw the diagram of (a) Bar magnet (b) Horse-shoe magnet.
Ans:

2.Identify magnetic and non-magnetic substances from the list given below: Iron, Steel, Nickel, Plastic, Wood, Copper and a Stainless Steel spoon
Ans:

3. Draw a diagram of a magnetic compass.
Ans:

4. Write main properties of a magnet.
Ans: (i) Magnet has two poles—south pole and north pole.
(ii) Poles of magnet cannot be isolated.
(iii) Like poles repel each other and unlike poles attract each other.
(iv) Freely suspended magnet aligns in N-S direction.

5.Write two methods by which a magnet can be demagnetised.
Ans: (1) By hammering the magnet strongly.
(2) By heating a magnet strongly and keeping it in the east-west direction.

6. It is advised to keep the magnets away from television, mobiles, CD and computers Explain why?
Ans: Television, mobiles, CD, computers and many more devices are made up of magnetic materials and magnets in it. If you bring a magnet closer to it then it will spoil these devices.

7. Few iron nails and screws got mixed with the wooden shavings while a carpenter was working with them.How can you help him in getting the nails and screws back from the scrap without wasting his time in searching with his hands?
Ans: With the help of a magnet we can attract all iron nails and screws and can separate them from the wooden shavings. As iron nails and screws are magnetic materials and will get attracted to the magnet,whereas wooden shavings are non-magnetic.

8. It is said that repulsion is a sure test for magnetism. Why is it so?
Ans: To identify the magnet, repulsion (like poles of two magnets repel) is the only test which will let you know whether the given rod is an iron rod or a bar magnet. Because a magnet attracts an iron object and unlike poles of magnets also attract each other.

9. A given bar magnet was broken into pieces. Where will be its North and South pole?

Ans: If you cut a bar magnet into pieces then the end labelled as North remains north and the other end formed will be south. Similarly the end that was pointing south will be south pole and its opposite end will be the new north pole.

10. You are given two rods. Out of these, one is an iron rod and the other one is magnet, how will you identify these rods?
Ans: Take both the rods and suspend them separately. Bring one end of a bar magnet close to both the ends of the suspended rod. If it shows attraction at both the ends then it is an iron rod. If it shows attraction at one end and repulsion at the other end then it is a bar magnet.

Class 6 Science Chapter 13 LONG ANSWER TYPE QUESTIONS

1. Show that a magnet has two poles. What are the properties of the poles of a magnet?
Ans. We know that pole is the point where the strength of the magnet is maximum. So more and more iron particles will be attracted at poles of a magnet when we bring a magnet near the iron particles. We will observe the crowdness of particles at the ends of magnet. This indicates the presence of two poles in a magnet. Hence poles are present in a magnet in pair. If a magnet is divided into two parts, each part also possesses a pair of poles.

 NCERT Solutions

Topics and Sub Topics in Class 6 Science Chapter 12 Electricity and Circuits:

Section Name	Topic Name
12	Electricity and Circuits
12.1	Electric cell
12.2	A bulb connected to an electric cell
12.3	An electric circuit
12.4	Electric switch
12.5	Electric conductors and insulators

NCERT Solutions for Class 6 Science Chapter 12 Electricity and Circuits

1. Fill in the blanks:
(a) A device that is used to break an electric circuit is called_______________
(b) An electric cell has___________
Ans:
(a) switch
(b) two

2. Mark ‘True’ or ‘False’ for the following statements:
(a) Electric current can flow through metals.
(b) Instead of metal wires, a jute string can be used to make a circuit.
(c) Electric current can pass through a sheet of thermocol.
Ans:
(a) True
(b) False
(c) False.

3.Explain why the bulb would not glow in the arrangement shown in fig

Ans: The bulb would not glow in the arrangement shown in figure because the one end of tester/screw driver is made up of plastic which does not allow the electric current to flow through it.

4. Complete the drawing shown in Fig. 12.9 to indicate where the free ends of the two wires should be joined to make the bulb glow.

Ans:

5. What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.
Ans: Electric switch is used to make electric circuit open or closed for a particular appliance and hence with the help of a switch we can use an appliance according

6. Would the bulb glow after completing the circuit shown in Fig. 12.9 if instead of safety pin we use an eraser?
Ans: No, since eraser is an insulator so it does not allow the current to pass. Hence the bulb will not glow.

7. Would the bulb glow in the circuit shown in Fig. 12.11.

Ans: Yes, the electric circuit is closed so the bulb will glow.

8. Using the“conduction tester” on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.
Ans: Yes, if the object is good conductor of electricity then current will pass through conduction tester and the bulb will glow. Hence the object will be a conductor of electricity.

9. Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.
Ans: Our body is good conductor of electricity and rubber is insulator. During repairing work if the body comes in contact with current carrying wire then there will not be any accident as rubber does not allow the passage of current through it. Hence electrician uses rubber gloves while repairing an electric switch.

10. The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
Ans: Plastic or rubber is an insulator which does not allow electric current to pass through it. The handles of the tools like screwdrivers and pliers used by electricians for repair have covering of plastic or rubber so that electric current may not pass through these tools to the body of the electrician to harm him.

Class 6 Science Chapter 12 VERY SHORT ANSWER TYPE QUESTIONS

1. What is the direction of flow of current in a dry cell?
Ans: . The current flows in closed circuit from +ve to -ve terminal of cell.

2. Name the +ve terminal of dry cell.
Ans:. Carbon rod with a metal cap on it.

3. Name the -ve terminal of a dry cell.
Ans:  Zinc metal plate.

4. What is dry cell?
Ans:  It is a device which converts chemical energy into electrical energy.

5. What is solar cell?
Ans: A device which converts solar energy into electrical energy.

6. What is open circuit?
Ans:  An electric circuit in which electrical contact at any point is broken is called open circuit.

7. Write one use of insulators.
Ans: Insulators are used in making switchboard, handles of testers, screw drivers.

8. What is the name of thin wire in the electric bulb?
Ans: Filament.

Class 6 Science Chapter 12 SHORT ANSWER TYPE QUESTIONS

1. Mention two advantages of a dry cell.
Ans: 
1. It converts chemical energy into electrical energy.
2. It is light and small in size.

2. Draw a diagram showing the two terminals of a bulb.
Ans:

3. Draw the circuit diagram for operating a bulb with the help of a dry cell.
Ans:

4. Define conductors and insulators. Give one example of each.
Ans:  A conductor is that which easily allows the passage of current through it. Example: Aluminium or any metal.
An insulator is that which does not allow the passage of current through it. Example: Rubber.

5. Identify conductors and insulators from the following:Eraser, paper, matchstick, copper wire, pencil lead, polythene
Ans: Conductors: Copper wire, pencil lead.
Insulator. Eraser, paper, matchstick, polythene.

6. Name the scientist who invented electric cell and the scientist who invented electric bulb.
Ans: Electric cell: Alessandro Volta.
Electric bulb: Thomas Alva Edison.

7. Give one activity to prove that air is an insulator.
Ans: Take an electric circuit, keep the terminals unconnected in the air. The bulb do not glow, as air is an insulator and does not allow the current to flow through it.

8. In any electric circuit, when the switch is on and the current flows through it why do the wire, switches, bulb or devices become hot?
Ans.: This is because electric energy changes into heat energy.

9.The headlights of a car have reflectors behind the bulb. What is the function of reflectors?
Ans: The reflector helps in reflecting the light into a focussed area.

10.If you touch an electric wire carrying current you get a shock, but if on the same wire the birds sit they do not get any shock/current. Explain why?
Ans: When we hold the wire carrying current then the circuit is closed and the current flows from our body and enters earth but the birds sitting on the same wire do not get any current as the circuit is not complete. If the bird touches the earth wire, it will also die due to electric shock.

Class 6 Science Chapter 12 LONG ANSWER TYPE QUESTIONS

1.(1)What is electric circuit?
(2)How many types of electric circuit are there? Define them.
(3)Draw a diagram to show the closed circuit for switch, bulb and dry cell.
Ans: 
(1)The diagram that shows the path of electric current is called electric circuit.
(2)There are two types of electric circuit:
(a) Open electric circuit
(b) Closed electric circuit
(a)Open electric circuit: The circuit in which electrical contact at any point is broken is called open electric circuit.
(b)Closed electric circuit: The circuit in which electric current flows from one terminal of a cell or battery to the other is called a closed circuit.

NCERT Solutions

NCERT Solutions for Class 6 Science Chapter 11 Light Shadows and Reflection

Topics and Sub Topics in Class 6 Science Chapter 11 Light Shadows and Reflection:

Section Name	Topic Name
11	Light, Shadows and Reflections
11.1	Transparent, opaque and translucent objects
11.2	What exactly are shadows?
11.3	A pinhole camera
11.4	Mirrors and reflections

1. Rearrange the boxes given below to make a sentence that helps us understand opaque objects.

Ans:

2. Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the fame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.
Ans:

3. Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
Ans: Yes, there are many things which give a circular shadow if held in one way and a rectangular shadow if held in another way. For example: a cylinder, a circular disc etc.

4. In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
Ans: No, in a completely dark room no image will be formed because there is no light in the room so no reflection of light takes place and no image will be formed.

Class 6 Science Chapter 11 VERY SHORT ANSWER TYPE QUESTIONS

1. Whether the moon is luminous or non-luminous body?
Ans: Moon is non-luminous body.

2. What is umbra?
Ans: Umbra is the dark region behind object facing light which does not receive light at all.

3. How does a light ray travel?
Ans: Light ray travels in a straight line.

4. Give one natural source of light. 
Ans: Sun is a natural source of light.

5. What is shadow? 
Ans: Shadow is the dark space behind an opaque object where light does not reach.

6. What is penumbra?
Ans: The less darker shadow formed penumbra.on the periphery of dark shadow is called penumbra.

Class 6 Science Chapter 11 SHORT ANSWER TYPE QUESTIONS

1. State difference between a luminous and a non-luminous body.
Ans: The bodies which emit light are called luminous bodies. Example: sun, stars, burning candle etc.
The bodies which does not emit light are called non-luminous bodies. Example: moon, earth, blackboard.

2. Why is the moon not considered as a luminous body?
Ans: Moon is non-luminous body because it shines by reflecting the sunlight falling on it.

3. What is an incandescent body? Give example.
Ans:  The bodies which emit light when heated to a very high temperature are called incandescent bodies. Example: electric bulb.

4. When does a shadow form?
Ans: Shadow is formed when light does not reach behind the opaque object kept in the path of light

5. Draw a diagram to illustrate the formation of umbra and penumbra.
Ans: 

6. What are the essential conditions for the formation of shadow?
Ans:
(1) There should be an opaque material.
(2) There should be a source of light and screen.
The object must be placed in the path of light. Then shadow is formed on the screen.

7. Define reflection of light.
Ans: When light rays after striking the smooth and shiny surface return to same medium, this phenomenon is called reflection of light.

8. Write difference between shadow and image.
Ans: 

9. How will you convert a glass sheet into a translucent sheet?
Ans: There are following two methods to convert glass sheet into a translucent sheet:
(i) By smearing a thin layer of oil on glass sheet.
(ii) By covering a side of sheet by butter paper.

10. What is shadow? How does the colour of an opaque object affects the colour of the shadow?
Ans: A dark outline or patch formed by an opaque object that blocks light coming from a source of light is called shadow. The colour of an opaque object does not affect the colour of the shadow.

11. Write the differences between umbra and penumbra.
Ans: 

12. What do we need in order to see a shadow?
Ans: We need: (i) A source of light (ii) a screen (in) an opaque object.

13. What do you mean by scattering of light?
Ans: When a beam of light falls on a rough surface it is turned back in different directions. It is called scattering of light.

14. A and B are facing the mirror and standing in such a way that A can see B and B can see A. Explain this phenomenon.

Ans:  The light rays from A falls on the mirror and gets reflected and reaches B, the light from B falls on the mirror and reflects to reach A. The path of light is just reversed as shown.

15. ‘X’ is 20 cm away from the mirror. If he moves few steps closer to the mirror what will happen to the image

Ans: The size of the image will be same as the size of the object.

16.Write the mirror image of ‘SMART’?
Ans: THAM8

17. Have you ever seen an ambulance? It is written in the form of mirror image on vehicles. Explain why it is done so and give the mirror image of AMBULANCE.
Ans:  The mirror image of AMBULANACE is aovt/yuaMA.
It is written so on the vehicles for the people to see in their rear view mirrors, read it correctly and immediately give way to the vehicle as it carries patients who need urgent medication.

18. You have to cost the shadow of your pencil on the wall with the help of candle in a dark room. How can you obtain the shadow of same size, small size and big size of the same pencil?
Ans: (a)The shadow of the pencil will be small when the pencil is taken close to the wall and away from the candle.
(b)The shadow will be big in size when the pencil is taken closer to the candle.
(c)To get the same sized shadow as the pencil is, adjust the distance between the wall, pencil and candle at equal distances.

Class 6 Science Chapter 11 LONG ANSWER TYPE QUESTIONS

1. What is reflection of light? Explain reflection of light with the help of an activity.
Ans:  When light rays fall on a highly polished (e.g. mirror) smooth surface and return to the same medium, it is called reflection of light.
Activity to show reflection of light: This activity should be done at night or in a dark room. Ask your friend to hold a mirror in his hand at one corner of the room. Stand at another comer with a torch in your hand. Cover the glass of torch with your fingers and switch it on. There should be small gap between your fingers. Direct the beam of torch-light on to the mirror that your friend is holding. Adjust the direction of torch so that patch of light falls on your friend standing in the room. This activity shows the reflection of light also that light travels in straight line.

2. Explain the manner in which light travels with the help of an activity.
Ans: Take a comb and fix it on one side of a thermacol sheet. Fix a mirror on the other side as shown in figure. Spread a dark coloured sheet of paper between the mirror and the comb. Send a beam of light from a torch through the comb. You get a pattern of light similar to that shown in figure. This activity explains the manner in which light travels and gets reflected from a mirror.

3. Explain that light has the property of rectilinear propagation.
Ans: We take three pieces of cardboard. Place them one on the top of one another and make a hole in the middle of each cardboard by using a thick nail. Erect these cards up on the table at a short distance away from each other. Take a candle which is of the same height as the holes in the cards. Light the candle and place it in front of the cards. We see that the light of candle is visible only when the holes on cards lie in a straight line. If we disturb them the light of candle disappears. This experiment shows that light propagates in a straight line.

NCERT Solutions

NCERT Solutions for Class 6 Science Chapter 10 Motion and Measurement of Distances

Topics and Sub Topics in Class 6 Science Chapter 10 Motion and Measurement of Distances:

Section Name	Topic Name
10	Motion and Measurement of Distances
10.1	Story of transport
10.2	How wide is this desk?
10.3	Some measurements
10.4	Standard Units of Measurements
10.5	Correct Measurement of Length
10.6	Measuring the length of a curved line
10.7	Moving things around us
10.8	Types of motion

1. Give two examples each of modes of transport used on land, water and air.
Ans:
(i) Land—Bus, truck, train.
(ii) Water—Ship, boat.
(iii) Air—Aeroplane, Helicopter.

2. Fill in the blanks:
(i) One metre is___________
(ii) Five kilometre is___________
(iii) Motion of a child on a swing is_____________ .
(iv) Motion of the needle of a sewing machine is_______________ .
(v) Motion of wheel of a bicycle is_____________ .
Ans:
(i) 100
(ii) 5000
(iii) periodic (oscillatory) motion
(iv) periodic oscillatory (v) circular.

3. Why can a pace or a footstep not be used as a standard unit of length?
Ans: Because a pace or a footstep of each and every person is not equal.

4. Arrange the following lengths in their increasing magnitude :
1 metre, 1 centimetre, 1 kilometre, 1 millimetre.
Ans: Ascending order of length:
1 millimetre < 1 centimetre < 1 metre < 1 kilometre

5. The height of a person is 1.65 m. Express it in cm and mm.
Ans:
(a) 1.65 m, as one metre = 100 cm
= 1.65 x 100 cm = 165 cm
(b)65 x 100 x 10 mm = 1650 mm.

6. The distance between Radha’s home and her school is 3250 ,m. Express this distance in km.
Ans:

7. While measuring the length of a knitting needle, the reading of the scale at one  end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?
Ans:  Length of the needle = 33.1 cm – 3.0 cm = 30.1 cm.

8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Ans: 
(i) Similarity: Both the wheel of a bicycle and a ceiling fan exhibit motion on a fixed axis.
(ii) Dissimilarity: Bicycle moves forward thus executes rectilinear motion but fan does not show such motion.

9. Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape?
Ans:  An elastic measuring tape gives incorrect length of the distance between two points.
Reasons:
(i) The length of the elastic tape varies and depends upon the force by which it is stretched.
(ii) Measurement would vary between 2 or 3 readings even when measured by the same person and by the same elastic tape.
(iii) Measurement would also vary if different persons measure the same distance.

10. Give two examples of periodic motion.
Ans:
(i) Oscillations of a pendulum.
(ii) Motion of swing/motion of earth round the sun.

Class 6 Science Chapter 10 VERY SHORT ANSWER TYPE QUESTIONS

1. Are senses reliable for accurate measurement?
Ans: Our senses are not reliable for accurate measurement.

2. Why can hand span and arm length not be used as standard units of length?
Ans: because these vary from person to person.

3. How many centimetres are there in 1 m?
Ans: 100 cm.

4. Name the measuring device which can be used for measuring the girth of a tree.
Ans: Measuring tape.

5. Give one example of linear motion.
Ans: Motion of stone falling from a certain height.

6. Give an example of circular motion.
Ans: Motion of arms of watch.

7. Name the types of motion in which a body moves along a straight path
Ans: Rectilinear or linear motion.

8.Find the length and breadth of given rectangle in mm and cm.

Ans: Using measuring scale (15 cm scale), Length AB = 3 cm and breadth BC = 2 cm.
AB = 3 x 10 = 30 mm
BC = 2 x 10 = 20 mm.

9.Give the unit for measuring the following:
(a) Distance between Delhi and Jaipur.
(b) Thickness of a coin.
(c) Length of your eraser.
(d) Length of your shoe lace.
Ans: 
(a) Kilometre
(b) Millimetre
(c) Centimetre
(d) Centimetre

10. Name the device used to measure the following:
(a) Size of your shoulder.
(b) Size of your wrist.
(c) Your height.
(d) Your weight.
(e) Cloth for curtain.
(f) Circumference of round table.
Ans: 
(a) Measuring tape
(b) Measuring tape
(c) Measuring tape
(d) Weighing balance
(e) Metre scale or measuring tape
(f) A long thread or measuring tape.

Class 6 Science Chapter 10 SHORT ANSWER TYPE QUESTIONS

1. State two precautions to be observed while measuring length with the help of a metre scale.
Ans:  Two precautions are:
(i) The initial point of distance must coincide with the zero reading of metre scale.
(ii) The eye should be kept in line with the point of measurement.

2. Define rest and motion.
Ans:  The objects which do not change their positions with time are said to be at rest. The objects which change their positions with time are said to be in motion.

3. Define the term standard unit.
Ans:  The unit that could be used everywhere as a basic unit of measurement is called a standard unit.

4. How can a measured length be expressed?
Ans: Each measurement has:
(i) A number describing the numerical value.
(ii) The unit in which that quantity is measured.

5. Give one example each of the following types of motion:

(a) Linear
(b) Translation
(c) Circular
(d) Periodic.
Ans:
Types of motion                  Example
(a)  Linear                                  motion of stone falling
(b)  Translatory                         buses
(c) Circular                                 ceiling fan
(d) Periodic                                pendulum of   clock

Class 6 Science Chapter 10 LONG ANSWER TYPE QUESTIONS

1. Why do we need standard unit for measurement?
Ans: We need standard unit for measurement to make our judgement more reliable and accurate. For proper dealing, measurement should be same for everybody. Thus there should be uniformity in measurement. For the sake of uniformity we need a common set of units of measurement, which are called standard units. Nowadays SI units are used in science and technology almost universally.

2. What type of motion do the following objects have?
(a) the galloping of a horse
(b) the needle of a sewing machine
(c) the movements of a mosquito
(d) the blades of an electric fan
(e) the smoke from a lighted dhoopbatti
(f) wheels of moving car.
Ans:
(a) The galloping of a horse: Linear motion.
(b) The needle of a sewing machine: Periodic motion.
(c) Movement of a mosquito: Random motion.
(d) Blade of an electric fan: Circular motion.
(e) The smoke from a lighted dhoopbatti: Random motion.
(f) Wheels of moving car: Linear motion and Rotational motion.

3. Give two examples for each of the following motions:
(i) Linear motion
(ii) Spinning motion
(iii) Oscillatory motion
(iv) Periodic motion 
(v) Vibrational motion
(vi) Circular motion
(vii) Random motion
Ans: 
(i) Linear motion: (a) Rolling of ball on ground, (b) Moving of bicycle on road,
(ii) Spinning motion: (a) Rotating fan, (b) Wheel of sewing machine.
(iii) Oscillatory motion: (a) Pendulum of clock, (b) Motion of a child on a swing,
(iv) Periodic motion: (a) Pendulum of clock, (b) Motion of a swing, heartbeat.
(v) Vibrational motion: (a) String of a guitar, (b) Surface of drums.
(vi) Circular motion: (a) Rotation of fan, (b) Bicycle wheel.
(vii) Random motion: (a) Motion of football players, (b) Movement of mosquito.

NCERT Solutions