Chapter 2: Motions of the Earth
Solved textbook questions with step-by-step explanations.
Grade 5 Q&A: Chapter 2: Motions of the Earth
Q1. What is rotation?
Answer: Rotation is the turning of an object around itself. Imagine a spinning top; it turns around an imaginary line passing through its center. This spinning motion is called rotation.
Q2. What is the Earth's axis? Is it straight or tilted?
Answer: The Earth's axis is the imaginary line around which it rotates. This axis passes through the North Pole, the center of the Earth, and the South Pole. The Earth's axis is not straight up and down; it is slightly tilted or inclined.
Q3. What are the Equator, Northern Hemisphere, and Southern Hemisphere?
Answer:
- The Equator is an imaginary circle drawn around the middle of the Earth, exactly halfway between the North and South Poles.
- It divides the Earth into two equal parts called hemispheres.
- The part of the Earth north of the Equator is the Northern Hemisphere.
- The part of the Earth south of the Equator is the Southern Hemisphere.
Q4. How does the Earth's rotation cause day and night?
Answer: The Earth rotates on its axis from west to east. As it rotates, different parts of the Earth face the Sun. The part of the Earth that gets light from the Sun experiences day. The part that is turned away from the Sun and is in darkness experiences night. This continuous turning is why we have a cycle of day and night.
Q5. What is revolution?
Answer: Revolution is the movement of the Earth in a fixed path (called an orbit) around the Sun. While the Earth is constantly rotating on its axis, it is also moving around the Sun. This motion is called revolution.
Q6. How long does one year take?
Answer: The time the Earth takes to complete one full revolution around the Sun is called one year. A year has about 365 days and 6 hours.
Q7. What is a leap year?
Answer: Since a year is 365 days and 6 hours long, we have 6 extra hours every year. In four years, these extra hours add up to 24 hours (6 hours × 4 = 24 hours), which is one full day. To account for this extra day, we add it to the calendar every fourth year. This year is called a leap year, and it has 366 days. The extra day is added to the month of February, which has 29 days in a leap year.
Q8. How are seasons caused?
Answer: Seasons are caused by the combination of two things: the Earth's revolution around the Sun and the tilt of its axis. Because the axis is tilted, as the Earth revolves, different parts of the Earth get more direct sunlight at different times of the year. When the Northern Hemisphere is tilted towards the Sun, it experiences summer, while the Southern Hemisphere experiences winter. The opposite happens six months later.
Q9. What are the phases of the moon?
Answer: The different shapes of the moon that we see in the sky are called the phases of the moon. The moon does not have its own light; it reflects sunlight. As the moon revolves around the Earth, we see different amounts of its sunlit part, which causes its shape to appear to change.
Q10. What is a Full Moon and a New Moon?
Answer:
- A Full Moon occurs when we see the entire sunlit side of the moon. The moon appears as a bright, complete circle in the sky.
- A New Moon occurs when the side of the moon facing us is not lit by the sun, so we cannot see the moon in the sky.
Q11. What is a lunar month and a tithi?
Answer: The time from one new moon to the next is about 28-30 days. This period is called a lunar month. A lunar month is divided into two fortnights (14-15 days each):
- Waxing Moon (Shukla Paksha): The period from the new moon to the full moon, when the visible part of the moon gets bigger each night.
- Waning Moon (Krishna Paksha): The period from the full moon to the new moon, when the visible part of the moon gets smaller each night.
Each day of the lunar month is called a tithi.
Solved Exercises (from Page 10)
1. What's the solution?
Question: Amit wants to take his granny to Australia which is in the southern hemisphere. But she cannot bear very cold weather. When should they make this trip?
Answer: Australia is in the Southern Hemisphere, which has seasons opposite to the Northern Hemisphere (where India is). When it is winter in India (around December to February), it is summer in Australia. Therefore, Amit should plan the trip to Australia between September and March, when the weather there will be warm and pleasant (summer).
2. Use your brain power!
(a) Question: How many rotations does the earth complete during one revolution around the sun?
Answer: The Earth completes about 365 rotations during one revolution around the sun. This is why there are about 365 days in a year.
(b) Question: It is sunrise at Itanagar in Arunachal Pradesh. Write the names of the following cities in the order in which the sun will rise there: Mumbai (Maharashtra), Kolkata (West Bengal), Bhopal (Madhya Pradesh), Nagpur (Maharashtra).
Answer: The Earth rotates from west to east, so the sun rises in the east first. We need to arrange the cities from east to west. Itanagar is the easternmost. The order for the given cities will be:
- Kolkata (West Bengal)
- Bhopal (Madhya Pradesh)
- Nagpur (Maharashtra)
- Mumbai (Maharashtra)
3. Fill in the blanks.
(a) The motion of the earth around itself is called rotation.
(b) The motion of the earth around the sun is called revolution.
(c) The rotation of the earth gives rise to day and night.
4. What is meant by each of the following terms?
(a) Full moon: The day when we see the complete, round, sunlit side of the moon from Earth.
(b) New moon: The day when the moon is between the Earth and the Sun, and the side facing us is not lit, so we cannot see the moon.
(c) Lunar month: The period of about 28 to 30 days from one new moon to the next. It includes one cycle of all the moon's phases.
(d) Tithi: Each day of a lunar month is called a 'tithi'.
5. Answer the following questions.
(a) Question: What is the equator?
Answer: The equator is an imaginary circle around the middle of the Earth, located at an equal distance from the North Pole and the South Pole.
(b) Question: What are the two parts of the earth made by the equator?
Answer: The equator divides the Earth into two equal parts: the Northern Hemisphere and the Southern Hemisphere.
Additional Questions and Answers
Q1. What is the name given to the changing shapes of the moon that we see?
Answer: The changing shapes of the moon that we see are called the phases of the moon
Q2. What are the names of the day on which we see a round moon and on which day we see no moon at all?
Answer: We see a round moon on the Full Moon day. We see no moon at all on the New Moon day
Q3. In which direction does the earth rotate?
Answer: The Earth rotates from west to east.
Q4. What is the duration of a year?
Answer: The duration of a year is about 365 days and 6 hours.
Q5. What is the revolution of the earth?
Answer: Revolution is the movement of the Earth in a fixed path (orbit) around the Sun. This motion, combined with the tilt of its axis, is what causes seasons.