1. What is the axis of the earth  ?

Ans. The axis of the earth is an imaginary line that passes through the centre of the earth and the two poles. 

2. What do you mean by rotation and revolution of the earth  ?

Ans. The spinning movement of the earth on its own axis is called rotation. The movement of the earth around the sun in its orbit is called revolution. 

3. Write a short paragraph to explain why a leap year has 366 days.

Ans. A year has 365 days , but the earth takes 365 days and 6 hours to complete one revolution around the sun.The extra 6 hours are added up.In four years these become 24 hours (6×4=24) that is equal to one day.This extra one day is added to the month of February , which makes 29 days in a leap year. Therefore leap year has 366 days.

4. Give two reasons why summer and winter happen .

Ans. The tilt of the earth’s  axis. 

The orbit of the earth around the sun. 

5. Why is northern hemisphere (a) hotter than the southern hemisphere during summer and  (b) colder than the southern hemisphere during winter  ?

Ans. (a) The northern hemisphere is hotter than the southern hemisphere during summer because it is tilted towards the sun and the sun rays fall directly on it. The southern hemisphere during the same time is tilted away from the sun and the sun rays fall less directly on it.

(b) The northern hemisphere is colder than the southern hemisphere during winter because it is tilted away from the sun and the sun rays fall less directly on it. The southern hemisphere during the same time is tilted towards the sun and the sun rays fall directly on it. 

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