Class 9 Science - Chapter Why Do We Fall ill NCERT Solutions | Conduct a survey in your neighbourhood t

Why are we normally advised to take bland and nourishing food when we are sick?

A baby is not able to tell her/his caretakers that she/he is sick. What would help us to find out
(a) that the baby is sick?
(b) what is the sickness?

What precautions can you take in your school to reduce the incidence of infectious diseases?

State any two conditions essential for being free of disease.

Under which of the following conditions are you most likely to fall sick?
(a) when you are taking examinations.
(b) when you have travelled by bus and train for two days.
(c) when your friend is suffering from measles.

Why?

In which of the following case do you think the long-term effects on your health are likely to be most unpleasant?
  •  if you get jaundice,
  •  if you get lice,
  •  if you get acne.

Why?

What are the different means by which infectious diseases are spread?

What are the immunisation programmes available at the nearest health centre in your locality? Which of these diseases are the major health problems in your area?

List any three reasons why you would think that you are sick and ought to see a doctor. If only one of these symptoms were present, would you still go to the doctor? Why or why not?

Are the answers to the above questions necessarily the same or different? Why?

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?

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

Who discovered cells, and how?

What is the acceleration of free fall?

What is the momentum of an object of mass m, moving with a velocity v?
(a) (mv)²      (b) mv²      (c) 1⁄2 mv²      (d) mv

Why is the plasma membrane called a selectively permeable membrane?

Explain with examples (i) Atomic number, (ii) Mass number, (iii) Isotopes and iv) Isobars. Give any two uses of isotopes.

An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the magnitude and direction of the velocity. If no, provide a reason.

Which organelle is known as the powerhouse of the cell? Why?

What does a neuron look like?

The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?

What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.

Why are manure and fertilizers used in fields?