 # physics numericals for class 9 sound with answers

Given below are the physics numericals for class 9 sound with answers
(a) Very shorts questions
(b) shorts questions
(d) Table Type questions

Question 1. Define one hertz?
Question 2.
Audible frequency range of a human ear is 20 hertz to 20000hertz. Express it in terms of time period?

Question 3.
Derive the relationship between wavelength, frequency and speed of sound?

Question 4.
A tuning fork having frequency 312Hz emits a wave which has a wavelength of 1.10m. Calculate the speed of sound?

Question 5.
A wave is moving in air with a velocity of 340m/s. Calculate the wavelength if its frequency is 512Hz?.

Question 6.
A radar signal is received $2 \times 10^{-5}$ sec. After it was sent and reflected by an aeroplane. How far is the aeroplane if speed of waves is $3 \times 10^8$ m/s?

Question 7. A sound wave has a frequency 2 kHz and wavelength 40 cm. How long will it take to travel 1.6 km?

Question 8.
Sound waves of wavelength $\lambda$ travel from a medium in which its velocity is v m/s into another medium in which its velocity is 3 v m/s. What is the wavelength of the sound in the second medium. Frequency remains constant?

Question 9.
A person is listening to a tone of 500 Hz sitting at a distance of 450m from the source of the sound. What is the time interval between successive compressions from the source? [Speed of sound in air = 330m/s]

Question 10.
A boy standing in front of a wall at a distance of 85 m 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.

Question 11.
A stone is dropped from a 500 m tall building into a pond. When is sound of splash heard at the top? (g=10m/s2 , speed of sound in air= 340m/s)?

Question 12.
Find the distance of cloud from you when you hear a thunder 3 sec after the lightning is seen. (given the speed of light= 3*108 m/s, speed of sound= 330m/s)? Why is lightning seen a few seconds before the thunder is heard during a thunderstorm?

Question 13.
In tank, 10 ripples are produced in one sec. If the distance between a crest and trough is 10cm, find?
(a)Wavelength
(b)Frequency
(c)Velocity of the wave?

Question 14.
When a wave travels from one medium to another, the wavelength changes but not the frequency. The wavelength of sound disturbance 30 cm in air and of the wave velocity is 340 m/s. What will be the wavelength of this disturbance in Helium? The speed of sound in helium is 970 m/s and 1450 m/s in water?

Question 15.
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.

Question 16
An echo is returned in 6 seconds. What is the distance of reflecting surface from source? [Given that speed of sound is 342 m/s.]

## Table Type Questions

Question 17. ## Summary

This physics numericals for class 9 sound with answers is prepared keeping in mind the latest syllabus of CBSE . This has been designed in a way to improve the academic performance of the students. If you find mistakes , please do provide the feedback on the mail. 