NCTB Class 7 Science Chapter 12 “The Solar System and Our Earth” Solution
Bangladesh Board Class 7 Science Solution Chapter 12 “The Solar System and Our Earth” Exercises Question and Answer by Experienced Teacher.
NCTB Solution Class 7 Chapter 12 “The Solar System and Our Earth”
|NCTB Bangladesh Board|
“The Solar System and Our Earth”
Fill in the blanks:-
(1) The sun is medium sized ——-.
(2) ——— planet is moving around the sun.
(3) The moon is the only —- satellite.
(4) We stay on the ——- of the earth.
(5) We do not fly off the earth due to —–.
Answer the following questions in brief:-
(1) Why did men think before that sun moves round the earth?
Answer:- The earth is moving round the sun but from the earth people observed with their bare eyes that in the morning the sun rises in the east but in the evening the sun sets in the west. So it seems from the earth that the sun moves round the earth from the east to the west. That’s why men thought before that sun moves round the earth.
(2) Who told about the earth centred model?
Answer:- Aristotle a great philosopher and scientist told about the earth centred model and then famous mathematician and (astrologer Ptolemy also told it).
(3) Explain how the sun and the other starts produce heat and light.
Answer:- The burning gases mixing with one another, turn stars contain mainly hydrogen and helium gas. The atoms of hydrogen gas mixing with one another, true into the atoms of helium. Lot energy is produced in this produces in this process and this energy speeds in the solar system as heat and light.
(4) What is comet? How is its tail created? Set an example of your acquainted comet?
Answer:- The comet is a luminary which is made of solid but it is turns into gas easily when it gets heat . When comets go near the sun then it is scattered in the sky turning into gas or solid due to the heat of the sun. Then it turns into a watchable tail.
An example of my acquainted comet is Halley’s Comet.
(5) Explain the earth’s two way motion citing an example.
Answer:- If we have certainly played with a top the we can observed that the top rotates, standing on the pointed head like the earth rotated on its own axis from west to east which is called earth’s diurnal motion. Other hand at the same time that top travels circular or elliptical way around the sun in its orbit which is called earth’s annual motion.
(7) Discuss the effect of change seasons over human being.
Answer:- Due to the changes of seasons we enjoy the seasons all the year, the weather is changing in order to the seasons, different crops grow. In cold countries most of the parts remain covered with ice, but in summer season when the ice melts the man is able to grow crops.
Multiple choice questions:-
(1) Which planet consists of ice and gas?
Answer:- (d) Uranus.
(2) The world which is applicable to the sun is —
Answer:- (c) (i) and (ii).
Answer the question no. 3 from the table below.
|Distance from the sun
Time of one rotation around the sun
|77.85||Approx. 12 years|
(3) The planet (that is not mentioned in the table) which has a distance of 22.8 crores km from the sun. Where is it situated?
Answer:- (d) In between Earth and Jupiter.
(a) What is diurnal motion?
Answer:- The earth takes 24 hours to rotate on its own axis from the west towards the east. The is called the earth’s Diurnal motion.
(b) Why does it rain heavily in Bangladesh in between June and July?
Answer:- It rains heavily in Bangladesh in between June and July because there has been down pouring due to monsoon wind and the rainy season is started.
(c) When do the smallest nights and longest days occur at southern hemisphere? Explain with the figure.
Answer:- 22nd December is the smallest nights and longest days occurs at souther hemisphere. This time, a part of southern hemisphere remains facing the sun. The sun shines vertically.