V Class - Science - III Term

Class : V Term - III Sub :- Science

1. FORCE AND WORK
Exercises:-

I. Answer the following questions
a. What is force?
Ans. A push or a pull applied on an object to make it move or to stop it from moving is called force.

b. Why do we use force?
Ans. We use force to stop or slow down a moving object or change the direction of a moving object.

c. Name and define the different kinds of forces with examples.
Ans. The different kinds of forces are:
1. Muscular Force :- The force applied by muscles is called muscular force.
Eg :- i. A bullock drawing a cart
ii. An elephant pulling a log.
2. Gravitational Force or gravity :- The force of the earth that pulls everything towards itself is called gravitational force or gravity.
Eg :- i. When a ball is thrown up, it falls to the ground.
ii. Fruits from a tree always fall to the ground.
3. Magnetic Force :- The force applied by a magnet on objects made of iron, nickel or cobalt to pull them towards it, is called magnetic force.
Eg :- Iron filings are pulled by a magnet.

d. What is work?
Ans. Work is said to be done if an object is displaced in the direction of force applied.
The product of force and displacement is work. W = f.s.

e. Why do we use machines ?
Ans. We use machines to __
i. Make our work easier
ii. Change the direction of force and
iii. Increase the speed of work.

f. What is a simple machine ? Name the various types of simple machines.
Ans. A simple machine is a tool that makes our work easier.
There are six types of simple machines. They are
1. Lever 2. Pulley 3. Wheel and Axle
4. Inclined plane 5. Screw 6. Wedge.

g. What is a lever ?
Ans. A lever is a straight rigid bar that can turn on a fixed point called the fulcrum.

h. Define i) Lever of first order ii) Lever of second order iii) Lever of third order.
Ans. i) Lever of first order :- If the fulcrum is in between the effort at
one end and the load on the other, such type of levers are called
first order levers.
Eg :- Claw hammer, scissors, crow bar, seesaw.
ii. Lever of the second order :- If the load is in between the fulcrum at one end and the effort on the other such type of levers are called second order levers.
Eg :- Bottle opener, nut cracker, wheel barrow
iii. Lever of the third order :- If the effort is applied in between the fulcrum at one end and load on the other, such type of levers are called third order lever.
Eg : Tongs, bread knives, tweezers, forceps.

i. What is a pulley ?
Ans. A pulley is a simple machine made of a grooved wheel (or a combination of grooved wheels) over which a rope, belt, chain or cable moves to raise, lower or move a heavy weight (load).

j. What is a wheel and axle arrangement ? Give some of its common examples.
Ans. Wheel and axle is a simple machine in which a wheel has a rod called an axle, passing through its centre in such a way that they turn together. It is used to lift or move a load. Eg :- Spinning wheel, toy car, egg beater, door knob, a top, screw driver.

Give reasons for the following :-
a. Claw hammer is a lever of the first order.
Ans. In claw hammer the fulcrum is in between the effort and the load.
So claw hammer is a lever of the first order.

b. We pull the pulley downwards but the loads get lifted upwards.
Ans. A pulley changes the direction of the force applied on the rope passing over it. So when we pull the pulley downwards, the loads get lifted upwards.

c. A screwdriver is an example of a wheel and axle arrangement.
Ans. The thick handle of the screwdriver works as the wheel and the thin metal rod acts as the axle. So screwdriver is an example of a wheel and axle arrangement.

1. Fill in the blanks (Reader)
a. Push, pull
b. force
c. muscular
d. gravitational force or gravity.
e. magnetic
f. work
g. simple machines
h. lever of the first order
i. scissors, seesaw
j. fulcrum and effort.
k. Third order
l. Effort, load
m. Pulley
n. Wheel and axle
o. Wedge

2. Write T for true and F for false (Reader)
a] False b] True c] False d] False e] True
F] True g] False h] False.

3. Choose the correct answer to fill in the blanks. (Reader)
a. direction
b. gravitational
c. second
d. third
e. wheel and axle

4. Match the following :-
a. claw hammer & scissors – levers of first order
b. bottle opener & nut cracker – levers of second order.
c. Tongs & forceps – levers of third order
d. Single fixed pulley – used to draw water from wells
e. Movable pulley – used to lift heavy loads in harbours
f. Screw – used to hold things together
g. Wedge – knives and axes.


2. THE EARTH AND THE MOON

1. Fill in the blanks (Reader) :
a. earth
b. distorted
c. 5515 Kg/m3
d. gravitational force
e. rotation of the earth
f. day, night
g. moon
h. craters
i. air
j. one - sixth
k. tide
l. transparent
m. opaque
n. shadows
o. eclipse

2. Write T for true and F for false (Reader).
a. false
b. true
c. false
d. true
e. false
f. false
g. true

3. Answer the following questions.
a. What are the conditions that make it possible for the earth to support life ?
Ans. The conditions that make it possible for the earth to support life are:
1. The earth is at the right distance from the sun, so it is neither too hot, nor too cold.
2. It is also of the right size to be able to hold on to its atmosphere.
3. Its atmosphere has oxygen and gives protection from the harmful rays of the sun.
4. It has the right combination of land and water.

b. What is the earth’s : i) mass ? density? iii) gravity?
Ans. i) The mass of the earth is 5.98 x 1024 Kg.
ii) The density of the earth is approximately 5515 Kg/ m3
iii) The gravity of the earth is 9.8 m/s2..

c. Define rotation and revolution of the earth.
Ans. Rotation :- The spinning of the earth from west to east on its own axis is called the rotation of the earth.
Revolution :- The movement of the earth around the sun in a fixed orbit is called the revolution of the earth.

d. How much time does the Moon take to rotate around the earth ?
Ans. The moon takes 27.3 days to rotate around the earth.


e. Why will a person weigh less on the moon ?
Ans. Gravity affects weight. The gravity of the moon is one - sixth of the gravity of the earth. So the weight of an object on earth will become one – sixth of its weight on the moon for e.g. A person with 36 kg weight will weigh only 6 kg on the moon.

f. What are tides ?
Ans. The way that the level of the sea regularly rises and falls during the day is
called tide.

g. How is a high tide caused ?
Ans. On the side of the earth facing the moon, the moon’s gravitational force pulls the water upwards towards it. This causes the water to rise up towards the moon causing high tide.
On the opposite side of the earth, the water similarly rises up due to the moon pulling the earth away from the water on that side causing high tide again.

h. How is low tide caused ?
Ans. As the water rises on the two sides of the earth by the moon’s pull, the water
In the other parts of the earth moves to these regions of high tides. As a result, the water level in these parts fall, causing low tide.

i. Define i) Transparent ii) Translucent objects iii) Opaque bodies.
Ans. i) Transparent :- The materials which allow the light to pass through them
are called transparent objects.
Ex: Glass
ii) Translucent objects :- The materials which allow the light to pass
through them partially are called translucent objects.
Ex :- Trace paper.
iv) Opaque bodies :- The materials which do not allow the light to pass
through them at all are called opaque bodies. E. Wooden plank

j. How is a shadow formed ?
Ans. A shadow is formed when an object blocks light from the sun or other light
source.

k. What is a solar eclipse ? How is it formed ?
Ans.1. On some new moon days, the sun, moon and the earth lie in a straight
line.
2. When the moon lies in between the sun and the earth, the shadow of the
moon falls on the earth.
3. It blocks the sun’s light as viewed from the earth making the sun
invisible.
4. This is called solar eclipse.

l. What is a lunar eclipse ? How is it formed ?
Ans. 1. On some full moon nights, the sun, the earth and the moon lie in the
same straight line.
2. Now the earth lies between the sun and the moon.
3. So, the moon passes through the shadow of the earth.
4. Thus the shadow of the earth falls on the moon making the moon
invisible.
5. If the entire moon is hidden by the shadow it is called total lunar eclipse
and if it is hidden partially it is called partial lunar eclipse.

3. Choose the correct answer to fill in the blanks.
3 a. Sun
b. Translucent
c. Transparent
d. Solar
e. Solar.

4. Match the following
a. Earth ______________________ densest planet
b. Moon ______________________ natural satellite
c. Sun ________________________ most important source of light
d. 24 hrs. _____________________ earth completes one rotation
e. 27.3 days __________________ moon completes one revolution.
f. Full moon day _______________ lunar eclipse.
g. New moon day ______________ solar eclipse.

5. Give reasons for the following :-
a. The earth is considered to be a special planet.
Ans. The earth is considered to be a special planet because it is the only planet which supports life.

b. There is no life on the moon.
Ans. The moon does not have an atmosphere so there is no air to breathe and moreover it doesn’t have water and air. So, life does not exist on the moon.

c. We can see the complete moon on a full moon day.
Ans. We can see the complete moon on a full moon day because the moon goes on
the far end side of the earth from the sun and the part of the moon facing the
earth receives complete sunlight.
d. Transparent object have no shadows.
Ans. A shadow is formed when on object blocks light from the sun or other light
source. As transparent objects allow the light rays to pass through them,
they do not cast any shadows.


3. SOIL EROSION AND CONSERVATION

1. Fill in the blanks (Reader)
a) Soil
b) Rats, snakes, earth worms
c) Erosion
d) Top fertile soil
e) Silt
f) Deforestation
g) Soil conservation
h) Terrace
i) Afforestation

2. Write T for true and F for false. (Reader)
a) F
b) T
c) F
d) T
e) T
f) T

3. Choose the correct answer to fill in the blanks (Reader)
Reptiles
Top soil
Infertile
Embankments
Deforestation.

4. Match the following (Reader)
Topsoil and subsoil – layers of the soil.
Soil erosion – causes infertility in soil.
Afforestation – planting many trees in an area of land.
Deforestation – cutting down of a large number of trees from an area
of land.
embankments – built where rivers strike the banks.
Terrace farming – employed in hilly areas.


5. Give reasons for the following :-
a. Soil is very important for life.
Ans. Plants grow in soil and are eaten by other animals. Many organisms live in the soil. These organisms excrete organic wastes into the soil. Decaying plant and animal matter makes the soil fertile. So soil is very important for life.

b. Trees help in preventing soil erosion
Ans. Trees help in preventing soil erosion as the roots of grass and
trees bind the soil firmly & protect it from being blown or washed away.

c. Embankments help in preventing soil erosion.
Ans. Embankments are sloping walls of earth or stones. They stop the soil from being carried away. They help in breaking and slowing down the flow of river water.

d. Terrace farming prevents soil erosion in hilly area.
Ans. When the water runs down the hilly slopes the furrows or terraces weaken the force with which the water flows down. As a result the amount of soil washed away is also reduced. This helps to prevent soil erosion.

6. Answer these questions.
a. What is soil?
Ans. The uppermost layer of the earth is called soil.

b. What are the various organisms that live in soil ?
Ans. Rodents like rats & mice, insects like millipedes, mites and bugs, reptiles like snakes, worms like earthworms, certain protozoa and spiders are some organisms commonly found in the soil.

c. What is top soil ?
Ans. The first layer of the soil is called top soil. It is very fertile as it contains humus.

d. What is soil erosion?
Ans. The phenomenon by which the layer of soil is worn away or lost by natural forces like wind and water is called soil erosion.

e. What are the various factors that cause soil erosion ? Explain.
Ans. The factors that cause soil erosion may be natural or man – made. The
Natural factors are:
Erosion by water :- When water hits the soil with force, it loosens and washes away the top soil.
Erosion by wind :- As the wind blows, the soil is carried away and gets deposited some where else.
Climatic changes :- Sudden change in climate for ex. Floods, heavy rains etc cause soil erosion.
Drought :- As the vegetation cover of soil dies, the soil becomes dry and loose and due to wind, soil erosion increases.

II. Man made factors
1. Deforestation :- Deforestation is the cutting down of a large number of trees from an area of land. When trees are cut down the soil is loosened and is then easily carried away by agents like water and wind.
2. Intensive farming :- As human population has increased farming has become more intensive resulting in excessive ploughing, use of fertilizers and irrigation. These factors damage the soil.
3. Urbanisation :- Urbanisation is the process by which towns and cities grow bigger as more and more people go to live in them. As a result human beings cut down forests for construction of houses and roads.
4. Overgrazing :- Overgrazing by animals remove the grass cover of soil. The exposed soil is quickly eroded by rain and wind.

f. What is deforestation ?
Ans. Deforestation is the cutting down of a large number of trees from an area of land for various purposes.

g. Mention the various ways by which soil can be conserved.
Ans. Soil can be conserved in many ways.
1. Planting trees and grass :- The roots of grass and trees bind
the soil firmly and protect it from being blown or washed away.

2. Making bunds and embankments :- Small walls made of mud or stone are constructed at places where the river strikes
the banks. These slowdown the flow of river water.

3. Terrace Farming or making furrows :- Areas of cultivation land on hill slopes are cut and levelled in the form of terraces or furrows. These furrows weaken the force with which the water flows down. As a result, the amount of soil washed away gets reduced.

4. Afforestation :- The process of planting many trees in an area of land is called afforestation. When rain water comes down with great force, it breaks against the leaves of trees and bushes. As a result its force gets reduced and it falls gently on the ground. This prevents the topsoil from being carried away by running water.

i. Define : (i) Terrace farming (ii) Afforestation (iii) bunds and embankments.
Ans. (i) Terrace farming :- Cutting and levelling of the hill slopes in the form of furrows or terraces and cultivating on these furrows is called terrace farming.
(ii) Afforestation :- The process of planting many trees in an area of land is called afforestation.
(iii) Bunds and embankments :- Sloping walls of earth or stone constructed at places where the river strikes the banks are called bunds or embankments.

j. What is Van Mahotsava ?
Ans. Van Mahotsava is the festival of trees, celebrated every year
throughout India in the 1st week of July (1st to 7th July). During this festival saplings of different species are planted all over the country.


4. AIR AND ITS IMPORTANCE

1. Fill in the blanks (Reader):-

a. mixture b] nitrogen c] oxygen
d] nitrogen e] carbondioxide f] weight, space
g] pressure h] troposphere I] stratosphere
j] mesosphere

2. Write T for true and F for false (Reader).
a. F
b. T
c. F
d. T
e. T

3. Choose the correct answer to fill in the blank (Reader).
a. Carbondioxide
b. Oxygen
c. Carbondioxide
d. Balloon
e. Warm
f. Troposphere
g. Global warming

4. Match the following (Reader)
a. Nitrogen – 78.03%
b. Oxygen – 20.95%
c. Carbondioxide – 0.03%
d. Argon – 0.93%
e. Hydrogen – 0.01%

5. Give reasons for the following :
a. Oxygen is vital for fife.
Ans. Living organisms need oxygen to live. They use oxygen to release energy from food. Oxygen is required for the process of burning something.

b. Plants need carbondioxide.
Ans. Plants use carbondioxide for preparing food by the process known as photosynthesis.

Answer the following questions.
a. What is air? What are its properties?
Ans. Air is a mixture of gases. The properties of air are:-
It occupies space.
It has weight.
It exerts pressure.

b. What is the composition of air?
Ans. Air contains mainly nitrogen (78%) and oxygen (about 21%). It also contains about 0.9% of argon, 0.03% carbondioxide and traces of other gases. Air also contains small quantities of dust and water vapour.

c. How is oxygen important to us?
Ans. 1. Living organisms need oxygen to live.
2. They use oxygen to release energy from food.
3. It is required for the process of burning.

d. How is nitrogen important for plants?
Ans. Nitrogen is essential for the growth of plants. It is used to make fertilizers.

e. Prove by an experiment that air has weight.
Ans. Let us take a plastic stick and two balloons. We need to inflate one of the balloons and tie it to one end of the stick . The other non-inflated balloon should be tied at the other end of the stick. We can see that the stick weighs down at the end where inflated balloon is tied. This proves that the inflated balloon is heavier than the other one. This is because of the air inside it which has weight.

f. What is atmosphere ?
Ans. The envelope of air surrounding the earth is called atmosphere.

g. What is atmospheric pressure ?
Ans. The pressure exerted by air is called atmospheric pressure.

h. What are the different layers of the atmosphere? Define each.
Ans. Troposphere, stratosphere, mesosphere, thermosphere & exosphere are the different layers of the atmosphere.
Troposphere :- The lowest layer of the atmosphere extending upto 10-15 kilometers above the surface of the earth where all weather changes takes place is called troposphere. It contains about 80% of all the gases in the atmosphere. This is the only layer where living things can breathe normally.

Stratosphere :- The layer of atmosphere above the troposphere which extends upto 50 Kilometers above the surface of the earth is called stratosphere. It contains a layer of ozone. The ozone layer absorbs the harmful radiations of the sun. Air crafts fly in this layer.

Mesosphere :- The layer of atmosphere which extends upto 80 Kilometers from the surface of the earth is called mesosphere. This layer has no clouds and the temperature is low.

Thermosphere :- The layer of atmosphere just above the stratosphere which extends upto 500 Kilometers from the surface of the earth is called thermosphere. Temperature in this layer is very high due to the sun’s heat. Space shuttles orbit in the thermosphere.

Exosphere :- The layer of atmosphere which merges into space where there are almost no gases is called exosphere.
i. Define i) Green house effect. ii) Global warming.
Ans. i. Green House effect :-When the content of carbondioxide is more in the atmosphere the carbondioxide traps the sun’s heat and prevents it from escaping. This is called the green house effect.
ii) Global warming :- Green house effect has lead to a gradual
increase in average climatic temperatures across the world. This
is called global warming.


5. OUR NATURAL RESOURCES

1. Fill in the blanks (Reader)
a. Natural resources
b. Renewable, Non – renewable
c. Erosion
d. Rotation
e. Forests
f. Sanctuaries
g. 88, 490
h. CNG
i. Coal, petroleum, metals

2. Write T for true and F for false (Reader).
a. T
b. F
c. T
d. F
e. F
f. F
g. T
h. F
i. T
j. T

3. Choose the correct answer to fill in the blanks (Reader).
a. natural
b. renewable
c. erosion
d. rotation
e. sanctuaries
f. public

4. Match the following (Reader).
a. wind, air and sun –---- renewable resources
b. minerals and natural gas ---- Non-Renewable resources
c. iron, zinc, copper & gold ---- metallic
d. oil, salt and mica –--- Non-metallic

5. Give reasons for the following :
a. Natural resources are very useful to us.
Ans. Natural resources are very useful to us because they provide water, air, land, forests, wild life, soil and minerals which are very essential for life.

b. If a farmer grows cereals in one season, he should grow beans, peas or pulses in the next season.
Ans. If a farmer grows cereals in one season, he should grow beans, peas or pulses in the next season because this will help to replace the nutrients, such as nitrogen, that were used up by the crops grown in the previous season. The fertility of the soil is thus restored. This helps to eradicate crop diseases.

c. We should use fuels like CNG.
Ans. We should use fuels like CNG because CNG is Eco-friendly and helps to check the emission of pollutants into the air.

6. Answer the following questions
a. What are natural resources?
Ans. Materials that occur in nature and are essential for human life are called natural resources.
b. Define i) Renewable resources ii) Non-renewable resources.
Ans. i) Renewable resources :- Natural resources like soil, forests, wild life, air, wind and water which are replenished naturally in the course of time and can be used repeatedly and continuously are called renewable resources.
ii) Non-renewable :- The resources which cannot be replenished by nature at the rate at which we use them are called non-renewable resources. Ex. Coal , petroleum etc.

c. What are the ways in which we can conserve soil ?
ans. 1. We must plant more trees. The roots of plants hold soil particles
together. This helps to prevent the fertile topsoil from being
washed away by heavy rainfall or floods.
2. Crop rotation :- Crop rotation is an agricultural practice by which different types of crops are grown in the same field season after season. This helps to replenish the lost nutrients in the soil. It helps to eradicate crop diseases.
3. Farmers should try and reduce use of chemical fertilisers.
4. Terrace farming prevents soil erosion in hilly areas.


d. Why are forests our national wealth?
Ans. 1. Forests are home to numerous plants that provide us with oxygen
and food.
2. They provide a safe habitat for a wide variety of animals.
3. They help to check floods and prevent soil erosion.
4. They maintain the balance in the environment.

e. How can forests be protected ?
Ans. Forests can be protected in the following ways.
1. Trees must not be, cut down or uprooted thoughtlessly.
2. More trees have to be planted.
3. Farmers must take steps to check overgrazing by cattle and goats.
4. Forest fires must be effectively controlled. They cause extensive damage to forests.
5. Awareness must be created among people about the importance of preserving forests.

f. How can we conserve wildlife?
Ans. The following steps can be taken to conserve our wild life.
1. Hunting, especially poaching of wild animals, should be prohibited.
2. More wild life sanctuaries have to be set up. They help to protect wild life in their natural habitat.
3. International and national organisations should take up projects that aim to conserve wild life.
4. Use of animal products like furs and skins should be strictly banned. Experiments like testing cosmetics on amimals should be banned too.

g. How can we prevent wastage of water?
Ans. We can prevent the wastage of water by taking the following steps.
1. We must repair leaking taps and pipes promptly.
2. We should close the tap after using the required amount of water.
3. We should harvest rainwater by making dams and barriages to store excess water, especially during the rainy season.

h. How can we prevent air pollution?
Ans. We can prevent air pollution by taking the following measures :-
1. We should try and use public transport as much as possible. This will help to bring down the number of vehicles on the roads.
2. Vehicles should be checked regularly to make sure that their emission levels are within permissible limits.
3. Vehicles should use eco-friendly fuels like CNG to check the emission of pollutants into the air.
4. Factories and industries should be away from residential areas.
5. We must create more awareness about the harmful effects of pollution.

i. What are minerals?
Ans. Minerals are Non-renewable natural resources that are obtained by
mining. Minerals can be either metallic or non-metallic.

j. What is over population? What are its effects?
Ans. The increase in the population of a place much beyond its natural
capacity is called overpopulation.

Effects :-
1. Over population leads to an imbalance in the relationship between the number of individuals in the area to the resources they need to survive in.
2. It leads to over crowding and depletion of natural resources.
3. As the population keeps increasing, more and more of the rural population keeps migrating to urban areas. This creates social problems.
4. Unemployment levels go up. Income levels of people come down. All these lead to antisocial activities.
5. More and more areas of land are being used up for constructing houses and roads. So the land available for cultivation becomes less and it leads to scarcity of food products.

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