# A Bullet Passes Past a Person at a Speed of 220 M S−1. Find the Fractional Change in the Frequency of the Whistling Sound Heard by the Person - Physics

Sum

A bullet passes past a person at a speed of 220 m s−1. Find the fractional change in the frequency of the whistling sound heard by the person as the bullet crosses the person. Speed of sound in air = 330 m s−1.

#### Solution

Given:
Velocity of bullet $v_s$= 220 ms−1
Speed of sound in air v = 330 ms−1
Let the frequency of the bullet be f.

Apparent frequency heard by the person $\left( f_1 \right)$ before crossing the bullet is given by:

$f_1 = \left( \frac{v}{v - v_s} \right) \times f$

On substituting the values, we get :

$f_1 = \left( \frac{330}{330 - 220} \right) \times f = 3f . . . . \left( 1 \right)$

Apparent frequency heard by the person $\left( f_2 \right)$ after crossing the bullet is given by :

$f_2 = \left( \frac{v}{v + v_s} \right) \times f$

On substituting the values, we get :

$f_2 = \left( \frac{330}{330 + 220} \right) \times f = 0 . 6f . . . . . \left( 2 \right)$

So,

$\left( \frac{f_2}{f_1} \right) = \frac{0 . 6f}{3f} = 0 . 2$

∴ Fractional change = 1 − 0.2 = 0.8
Concept: Speed of Wave Motion
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#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 16 Sound Waves
Q 67 | Page 356