(English Medium) ICSE Class 9 - CISCE Question Bank Solutions

Answer the following question :
Can sound travel in vacuum?

The sound of an explosion on the surface of a lake is heard by a boat man 100 m away and by a diver 100 m below the point of explosion.

(i) Who would hear the sound first: boatman or diver?

(ii) Give a reason for your answer in part (i).

(iii) If sound takes time t to reach the boatman, how much time approximately does it take to reach the diver? 

Describe a simple experiment to determine the speed of sound in air. What approximation is made in the method described by you? 

Complete the following sentences :

Sound cannot travel through __________, but it requires a ___________.

Complete the following sentences :

Wave velocity = ________________ × wavelength.

The speed of sound in air at 0°C is nearly :

The speed of light in air is :

The heart of a man beats 75 times a minute. What is its (a) frequency and (b) time period? 

The separation between two consecutive crests in a transverse wave is 100 m. If wave velocity is 20 m s^-1, find the frequency of wave. 

An observer A fires a gun and another observer B at a distance 1650 m away from A hears its sound. If the speed of sound is 330 m s^-1, find the time when B will hear the sound after firing by A. 

An observer sitting in line of two tanks watches the flashes of two tanks firing at each other at the same time, but he hears the sounds of two shots 2s and 3.5s after seeing the flashes. If distance between the two tanks is 510m, find the speed of sound. 

What do you mean by the audible range of frequency? 

Select the correct option.

Unit of thrust in the SI system is

Select the correct option.

The unit Nm² is the unit of