Question

Two boys stand close to a long straight metal pipe and some distance from each other. One boy fires a gun and the other hears two explosions, with a time interval of one second between them. If the velocity of sound in metal is $3630m{s}^{-1},$ the distance between the two boys is

• A. 36.3 m
• B. 7.26 m
• C. 363 m
• D. 3630 m

Answer 1

Answer: (C)

$t_{\text{air }}=\frac{d}{330m/s};t_{\text{metal }}=\frac{d}{3630m/s}$
$t_{\text{air }}-t_{\text{metal }}=1;$
$\Rightarrow d\left[\frac{1}{330}-\frac{1}{3630}\right]=1$
$\Rightarrow d=\frac{3630\times 330}{(3630-330)}$
$=\frac{3630\times 330}{3300}\simeq 363m$