# Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board chapter 12 - Study of Sound [Latest edition]

## Chapter 12: Study of Sound

Exercise
Exercise [Page 137]

### Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board Chapter 12 Study of Sound Exercise [Page 137]

Exercise | Q 1.1 | Page 137

Fill in the blank and explain

Sound does not travel through …………

Exercise | Q 1.2 | Page 137

Fill in the blank and explain

The velocity of sound in steel is …............ than  the velocity of sand in water.

Exercise | Q 1.3 | Page 137

Fill in the blank and explain

The incidence of ……… in daily life shows that the velocity of sound is less than the velocity of light.

Exercise | Q 1.4 | Page 137

Fill in the blank and explain

To discover a sunken ship or objects deep inside the sea, ....................... technology is used.

Exercise | Q 2.1 | Page 137

Explain giving scientific reason.

The roof of a movie theatre and a conference hall is curved.

Exercise | Q 2.2 | Page 137

Explain giving scientific reason.

The intensity of reverberation is higher in a closed and empty house.

Exercise | Q 2.3 | Page 137

Explain giving scientific reason.

We cannot hear the echo produced in a classroom.

Exercise | Q 3.1 | Page 137

Answer the following question in your own words.

What is an echo? What factors are important to get a distinct echo?

Exercise | Q 3.2 | Page 137

Answer the following question in your own words.

Study the construction of the Golghumat at Vijapur and discuss the reasons for the multiple echoes produced there.

Exercise | Q 3.3 | Page 137

Answer the following question in your own words.

What should be the dimensions  and the shape of classrooms so that no echo can be produced there?

Exercise | Q 4 | Page 137

Where and why are sound absorbing materials used?

Exercise | Q 5.1 | Page 137

Solve the following example.

The speed of sound in air at 0°C is 332 m/s. If it increases at the rate of 0.6 m/s per degree, what will be the temperature when the velocity has increased to 344 m/s?

Exercise | Q 5.2 | Page 137

Solve the following example.

Nita heard the sound of lightning after 4 seconds of seeing it. What was the distance of the lightning from her?   (The velocity of sound in air is 340 m/s?) (Ans: 1360 m)

Exercise | Q 5.3 | Page 137

Solve the following example.

Sunil is standing between two walls. The wall closest to him is at a distance of 360 m. If he shouts, he hears the first echo after 4 s and another after another 2 seconds.

1.What is the velocity of sound in air?
2.  What is the distance between the two walls?

(Ans: 330 m/s; 1650 m)

Exercise | Q 5.4 | Page 137

Solve the following example.

Hydrogen gas is filled in two identical bottles, A and B, at the same temperature. The mass of hydrogen in the two bottles is 12 gm and 48 gm respectively. In which bottle will sound travel faster? How may times be as fast as the other?

(Ans: In A; Twice)

Exercise | Q 5.5 | Page 137

Solve the following example.

Helium gas is filled in two identical bottles A and B. The mass of the gas in the two bottles is 10 gm and 40 gm respectively. If the speed of sound is the same in both bottles, what conclusions will you draw? (Ans:  Temperature of B is 4 times the temperature of A.)

Exercise

## Balbharati solutions for Science and Technology 9th Standard Maharashtra State Board chapter 12 - Study of Sound

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Concepts covered in Science and Technology 9th Standard Maharashtra State Board chapter 12 Study of Sound are Sound, Propagation of Sound, Characteristics of a Sound Wave, Speed of Sound (Velocity of Sound), Speed of Sound in Different Media, Properties of Sounds, Audibility and Range, Ultrasonic Sound Or Ultrasound, Reflection of Sound, Echoes, Reverberation, SONAR, Sonography, Human Ear.

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