Maharashtra Board Class 5 EVS Part I Chapter 2 Motions of the Earth PDF Download

Motions Of The Earth

The Earth's Rotation

Take a globe like the one in the picture and spin it. Note the line around which it rotates. Now take a plumb-line and hold it close to the globe as shown in the picture. If you cannot get a plumb-line, tie a long thread to an eraser and make one.

You will see that the plumb-line and the earth's axis are at an angle to each other. That is, the earth's axis is inclined.

Rotation

Take a top. Spin it and observe its movement.

The top turns around itself. Any object that turns about itself actually turns around a certain imaginary line. The turning of an object around itself is called rotation and the imaginary line around which it rotates is called its axis of rotation.

Teacher's Note

When you spin a top or a globe, it moves around its own line. This is like how a merry-go-round spins around its center pole in a park near your home.

Exam Trick

Remember: Rotation means turning around itself. Just like you spin around your own body in a game, the earth also spins around its own axis.

Points To Remember

Rotation is when something turns around itself.
The imaginary line is called the axis of rotation.
The earth rotates around an imaginary line called its axis.

The earth rotates with its axis inclined like this. The line NS in the picture shows the earth's axis. It passes through the centre of the earth. The points N and S are called the poles of the earth. N is the north pole of the earth and S is the south pole.

If a circle were drawn around the surface of the earth exactly in between the north and south poles, it would divide the earth into two equal parts. This imaginary circle is called the equator. The two equal parts it makes of the earth are called the northern hemisphere and the southern hemisphere respectively.

Teacher's Note

The equator divides the earth into two parts. It is like an imaginary line drawn around the middle of the earth, just like how your waist divides your body into upper and lower parts.

Exam Trick

Remember: Equator = Equal parts. It divides the earth equally into north and south hemispheres.

Points To Remember

The axis passes through the center of the earth.
N is the north pole and S is the south pole.
The equator divides the earth into northern and southern hemispheres.
Each hemisphere is an equal part of the earth.

Day And Night On The Globe

Stand a candle in the middle of a large table. Draw a big circle around the candle. Place a globe at any point on this circle. Light the candle. See that it is dark in the room. Suppose that the candle is the sun.

Observe which part of the globe gets the sun's light and which one does not.

Now, looking at the globe from the direction of the north pole, turn it anti-clockwise. This is how the earth rotates, i.e. it rotates from west to east. As the earth rotates, its different parts come into the light of the sun one after the other and turn away from it also in the same order.

Sunset And Sunrise

Stick a red bindi on the globe. Set up the previous model of the globe and the candle. Turn the globe anti-clockwise. Note when it is sunrise, noon and sunset at the location of the bindi.

After one sunrise, note when the next one occurs at the bindi. You will see that this happens when the earth completes one rotation, that is, when it makes one complete turn around itself.

This period of time that the earth takes to complete one rotation is called a day. A day has two parts, daytime and nighttime or simply day and night. For the purpose of measuring time, we divide the whole day into 24 parts, each of which is called an hour.

Teacher's Note

When the earth rotates, the part facing the sun sees day and the other part sees night. In India, when it is daytime in Delhi, it is nighttime on the other side of the earth.

Exam Trick

Remember: One rotation = One day = 24 hours. When the earth completes one full spin, one day passes.

Points To Remember

Day and night are caused by the earth's rotation.
A day has 24 hours.
The well-lit part of the globe shows day.
The dark part shows night.

A Year

Now, move the globe along the circle on the table. As you do this, keep rotating the globe and ensure that the axis does not change its orientation. Eventually, the globe will come back to its original place on the circle. This is how the earth revolves around the sun even as it rotates around itself. The period of time the earth takes to complete one revolution around the sun is called one year. There are about 365 days and 6 hours in a year.

Teacher's Note

The earth takes 365 days to go around the sun once. That is why our year has 365 days, just like how the calendar on your wall shows the year.

Exam Trick

Remember: One revolution = One year. The earth moves around the sun and comes back to the same place after 365 days.

Points To Remember

Revolution means moving around the sun.
One revolution takes 365 days and 6 hours.
The earth rotates while it revolves around the sun.
The axis stays tilted during the entire revolution.

You know that the length of day and night is not always equal. This happens because of the earth's inclined axis and its revolution around the sun.

In the northern hemisphere, between 22 March and 23 September, the days are longer than the nights. Therefore, it is warmer there. That is, it is summer in the northern hemisphere. However, during this same period in the southern hemisphere, the nights are longer than the days. The earth gets less heat in these parts and therefore it is winter in the southern hemisphere.

In the period from 23 September to 22 March, the days are longer than the nights in the southern hemisphere. It gets more heat and it is summer there. In this period in the northern hemisphere, it is the nights that are longer. The northern hemisphere gets less heat and it is winter there.

Note that there may be differences in these dates due to the leap year. In India, summer, the rainy season and winter are considered to be the main seasons. We also divide the year into six seasons, namely, Vasant, Grishma, Varsha, Sharad, Hemant and Shishir.

This cycle of six seasons is called the rituchakra. Many of our festivals are connected with the seasons. Many of our songs and games are also related to the different seasons.

Teacher's Note

The seasons change because the earth is tilted. In India, we have six seasons in the year, not just four. The monsoon season is very important for Indian farmers.

Exam Trick

Remember: Summer in North = Winter in South at the same time. When it is hot in Delhi, it is cold in Australia.

Points To Remember

Days and nights are not always equal in length.
This is because of the earth's tilted axis.
When one hemisphere has summer, the other has winter.
India has six seasons in the year.
The six seasons together are called rituchakra.

The Full Moon And The New Moon

The moon revolves around the earth and the earth revolves around the sun. However, these two orbits intersect. Hence, the sun, the moon and the earth are not always along a straight line.

We see half of the moon's surface which faces the earth. That is, from the earth we see only one side of the moon. The moon has no light of its own. We can see the moon because of the sun's light that falls on it. On a full moon night, we see the entire side of the moon that faces the earth. On a new moon night, we cannot see any of it.

From the full moon to the new moon the illuminated part of the moon seen from the earth becomes smaller and smaller. From new moon to full moon it again grows bigger and bigger. These different shapes of the moon that we see are called the phases of the moon.

Teacher's Note

The moon does not have its own light. We see it because the sun's light falls on it. On Diwali night, we see the full moon which is completely bright.

Exam Trick

Remember: Full moon = bright and round. New moon = you cannot see it at all. It is like the moon hides behind the sun.

Points To Remember

The moon revolves around the earth.
The moon has no light of its own.
We see the moon because of the sun's light.
Full moon night shows the entire bright side of the moon.
New moon night shows no moon at all.

The Lunar Month And Days (Tithi)

You know that it takes 14 or 15 days from new moon to full moon. This is the fortnight of the waxing moon. After the full moon, the moon appears smaller and smaller and after 14 to 15 days it is new moon again. This period is the fortnight of the waning moon. Thus, the period from one new moon to the next is of 28 to 30 days. It is called the lunar month. Every day of the lunar month is called a tithi.

Teacher's Note

Our Indian calendar is based on the moon's movement, not just the sun. The days of the lunar month are called tithis and are used in India for festivals and prayers.

Exam Trick

Remember: Lunar month = 28 to 30 days. It goes from new moon to full moon to new moon again. Each day in this month is called a tithi.

Points To Remember

It takes 14 to 15 days from new moon to full moon.
It takes 14 to 15 days from full moon to new moon.
One lunar month = 28 to 30 days.
Each day of the lunar month is called a tithi.
The waxing moon is the moon growing bigger and the waning moon is the moon growing smaller.

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