Numericals for Class 9 Science Chapter 12 Sound

Numericals for Class 9 Science Chapter 12 Sound

Q.1. A boy hears an echo of his own voice from a distant hill after 1 s. the speed of sound is 340m/s. What is the distance of the hill from the boy?

Q.2. An engine is approaching a hill at constant speed. When it is at a distance of 0.9km, it blows a whistle, whose echo is heard by the driver after 5s. If the speed of sound is 340m/s, calculate the speed of the engine.

Q.3. A ship which is stationary, is at a distance of 2900 m from the seabed. The ship sends an ultrasound signal to the seabed and its echo is heard 4s. Find the speed of sound in water.

Q.4. A man fires a shot and hears an echo from a cliff after 2s. He walks 85m towards the cliff and the echo of a second shot is now heard after 1.4s What is the velocity of sound and how far was the man from the cliff when he first heard the echo?

Q.5. A boy hears an echo of his own voice from a distant hill after 2.5 s. the speed of sound is 340m/s. Calculate the distance of the hill from the boy.

Q.6. A person clapped his hands near a cliff and heard the echo after 5 s. What is the distance of the cliff from the person if the speed of the sound, v is taken as 346 m/s?

Q.7. A boy is standing in front of wall at a distance of 85m produces 2 claps per second. He notices that the sound of his clapping coincides with the echo. The echo is heard only once when clapping is stopped. Calculate the speed of sound.

Q.8. A sonar device on a submarine sends out a signal and receives an echo 5s later. Calculate the speed of sound in water if the distance of the object from the submarine is 3625m.

Q.9. A man stationed between two parallel cliffs fires a gun. He hears the first echo after 1.5 s and the next after 2.5 s. What is the distance between the cliffs and when does he hear the third echo? Take the speed of sound in air is 340 m/s.

Q.10. A child hears an echo from a cliff after the sound of powerful cracker is produced. How far away is the cliff from the child? (Take speed of the sound in air as 340 m/s).

Q.11. An observer standing between two cliffs fires a gun. He hears one echo after 1.5 s and another after 3.5 s. If the speed of sound is 340 m/s, find (a) the distance of the observer from the first cliff and (b) distance between the cliffs.

Q.12. A boy stands 60m in front of a tall wall and claps. The boy continues to clap every time an echo is heard. Another boy finds that the time between the first (1st) and the fifty first (51st) clap is 18s. Calculate the speed of the sound.

Q.13. A person standing between two vertical cliffs and 680m away from the nearest cliff, shouted. He heard the first echo after 4s and the second echo 3s later. Calculate (a) the speed of sound in air and the distance between the two cliffs.

Q.14. A man standing at 51m from a wall fires a gun. Calculate the time after which an echo is heard. The speed of sound is 340 m/s.

Q.15. A man fires a gun towards a hill and hears its echo after 5s. He then moves 340m towards the hill and fires his gun again. This time he hears the echo after 3s. Calculate the speed of the sound.

Q.16. A ship sends out ultrasound that returns from the seabed and is detected after 3.42s. If the speed of the ultrasound through sea water is 1531 m/s, what is the distance of the seabed from the ship?

Q.17. A sonar emits pulses on the surface of water which are detected after reflection from its bottom at a depth of 1531m. If the time interval between the emission and detection of the pulse is 2s, find the speed of sound in water.

Q.18. A sonar device on a submarine sends out a signal and receives an echo 10 s later. Calculate the speed of sound in water if the distance of the object from the submarine is 7650m.

Q.19. It takes 2.4a to record the echo of a sonar. If the speed of sound in water is 1450 m/s, find the depth of the ocean floor.

Q.20. A man standing at 68m from a wall fires a gun. Calculate the time after which an echo is heard. The speed of sound is 340 m/s.

Integer Type Numerical Problems for Class 9 Science Chapter 12 Sound

In this section, each question, when worked out will result in one integer from 0 to 9 (both inclusive)

Q.21. A person lives at a distance of 1.32 km from a factory. If the speed of sound in air be 330 m/s, how much time will the sound of factory siren takes to reach the worker?

Show Answer

$$ \begin{aligned} & \text { (4) : Displacement }=1.32 \mathrm{~km}=1320 \mathrm{~m} \\ & \text { Velocity of sound }=330 \mathrm{~m} \mathrm{~s}^{-1} \\ & \text { We have velocity }=\frac{\text { displacement }}{\text { time }} \\ & =\frac{1320 \mathrm{~m}}{330 \mathrm{~m} \mathrm{~s}^{-1}}=4 \mathrm{~s} \\ & \end{aligned} $$

---

Q.22. A boy stands 165 m in front of a high wall and then blows a whistle. Calculate the time interval when he hears an echo (speed of sound = 330 m/s)

Show Answer

t = 1 s

---

Q.23. The speed of sound is 330 m/s and that of light is 3 x 10⁸ m/s. The ratio of speed of sound to that of light is 11:10^x. Find the value of x.

Show Answer

x = 7

---

Q.24. The distance of a reflecting surface from a source is 513 m, and speed of sound is 342 m/s. Find the time in which the echo return.

Show Answer

3 s

---

Q.25. A sound wave has a frequency 1000 Hz and speed 320 m/s. How long will it take to move through 1 km.

Show Answer

3 s

---

You may also like:

Download Books – Exam Special

CBSE Books	ICSE Books
OLYMPIAD Books	FOUNDATION Books
JEE Books	NEET Books

➡ Click below titles to expand