Class 9 Science - Chapter Natural Resources NCERT Solutions | What are the methods of preventing or re

List any three human activities that you think would lead to air pollution.

What causes winds?

Why is the atmosphere essential for life?

Why do organisms need water?

Why is water essential for life?

We know that many human activities lead to increasing levels of pollution of the air, water-bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution?

List any three human activities which would lead to an increase in the carbon dioxide content of air.

How does the atmosphere act as a blanket?

How is our atmosphere different from the atmospheres on Venus and Mars?

You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather?

Which of the following has more inertia: (a) a rubber ball and a stone of the same size? (b) a bicycle and a train? (c) a five-rupees coin and a one-rupee coin?

State the universal law of gravitation.

Which of the following are matter?

Chair, air, love, smell, hate, almonds, thought, cold, cold-drink, smell of perfume.

A force of 7 N acts on an object. The displacement is, say 8 m, in the direction of the force (Fig. 11.3). Let us take it that the force acts on the object through the displacement. What is the work done in this case?

What is meant by a pure substance?

How does the sound produced by a vibrating object in a medium reach your ear?

In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g water and 8.2 g of sodium observations are in agreement with the law of conservation of mass.

sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water

What are canal rays?

State any two conditions essential for good health.

Who discovered cells, and how?

What is a tissue?

What is the nature of the distance-time graphs for uniform and non-uniform motion of an object?

Why is ice at 273 K more effective in cooling than water at the same temperature?

Write the distribution of electrons in carbon and sodium atoms.

A doctor/nurse/health-worker is exposed to more sick people than others in the community. Find out how she/he avoids getting sick herself/himself.

Compare the properties of electrons, protons and neutrons.

An artificial satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the earth.

In what direction does the buoyant force on an object immersed in a liquid act?

What produces more severe burns, boiling water or steam?

Give reason for the following observations.

(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume sitting several metres away.