Class 9 Science - Chapter Sound NCERT Solutions | Explain the working and application of a

Explain how sound is produced by your school bell.

Explain how defects in a metal block can be detected using ultrasound.

Distinguish between loudness and intensity of sound.

A sound wave travels at a speed of 339 m s^-1. If its wavelength is 1.5 cm, what is the frequency of the wave? Will it be audible?

Which characteristic of the sound helps you to identify your friend by his voice while sitting with others in a dark room?

Which wave property determines
(a) loudness,    (b) pitch?

A sonar device on a submarine sends out a signal and receives an echo 5 s later. Calculate the speed of sound in water if the distance of the object from the submarine is 3625 m.

Explain how the human ear works.

How is ultrasound used for cleaning?

Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?

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?

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.

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

Who discovered cells, and how?

Differentiate between striated, unstriated and cardiac muscles on the basis of their structure and site/location in the body.

What are the advantages of classifying organisms?

What are macro-nutrients and why are they called macro-nutrients?

Define valency by taking examples of silicon and oxygen.

What does the path of an object look like when it is in uniform motion?

A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer.

What are the advantages of composite fish culture?

Which do you think is a more basic characteristic for classifying organisms?

(a) the place where they live.
(b) the kind of cells they are made of. Why?

A motorcar of mass 1200 kg is moving along a straight line with a uniform velocity of 90 km/h. Its velocity is slowed down to 18 km/h in 4 s by an unbalanced external force. Calculate the acceleration and change in momentum. Also calculate the magnitude of the force required.

What is pasturage and how is it related to honey production?