Class 9 Science - Chapter Natural Resources NCERT Solutions | What is soil erosion?

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?

Two children are at opposite ends of an aluminium rod. One strikes the end of the rod with a stone. Find the ratio of times taken by the sound wave in air and in aluminium to reach the second child.

Describe with the help of a diagram, how compressions and rarefactions are produced in air near a source of sound.

If number of electrons in an atom is 8 and number of protons is also 8, then (i) what is the atomic number of the atom? and (ii) what is the charge on the atom?

Why are manure and fertilizers used in fields?

How are the criteria for deciding divisions in plants different from the criteria for deciding the subgroups among animals?

What are the functions of the stomata?

Who discovered cells, and how?

Complete the following table.

Look at the activities listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.
  • Suma is swimming in a pond.
  •  A donkey is carrying a load on its back.
  •  A wind-mill is lifting water from a well.
  •  A green plant is carrying out photosynthesis.
  •  An engine is pulling a train.
  •  Food grains are getting dried in the sun.
  •  A sailboat is moving due to wind energy.

If an atom contains one electron and one proton, will it carry any charge or not?