Class 9 Science - Chapter Sound NCERT Solutions | Explain how sound is produced by your sc

Explain the working and application of a sonar.

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?

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.

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

How is ultrasound used for cleaning?

Explain how the human ear works.

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?

A racing car has a uniform acceleration of 4 m s^-2. What distance will it cover in 10 s after start?

List the points of differences between homogeneous and heterogeneous mixtures.

In the hierarchy of classification, which grouping will have the smallest number of organisms with a maximum of characteristics in common and which will have the largest number of organisms?

What does a neuron look like?

What is the mass of—

(a) 1 mole of nitrogen atoms?
(b) 4 moles of aluminium atoms (Atomic mass of aluminium = 27)?
(c) 10 moles of sodium sulphite (Na₂SO₃)?

How many types of elements together make up the xylem tissue? Name them.

How does the cork act as a protective tissue?

Name the following.

(a) Tissue that forms the inner lining of our mouth.
(b) Tissue that connects muscle to bone in humans.
(c) Tissue that transports food in plants.
(d) Tissue that stores fat in our body.
(e) Connective tissue with a fluid matrix.
(f) Tissue present in the brain.

A pair of bullocks exerts a force of 140 N on a plough. The field being ploughed is 15 m long. How much work is done in ploughing the length of the field?

Why is it advised to tie any luggage kept on the roof of a bus with a rope?