Question

what is the least distance at which one has to stand from a cliff to hear an echo? Given that speed of the sound in air is 346ms-1​

Answer 1

Answer :-

Given :-

• Distance = 2d ( because echo is the reflected sound )

• Velocity = 346 m/s

• Time = 0.1 second ( because any sound persists for 0.1 second in ear )

To Find :-

• d

Solution :-

We know that,

Distance = Speed × Time

Substituting the values :-

→ 2d = v × t

→ 2d = 346 × 0.1

→ 2d = 34.6

→ d = 34.6 / 2

→ d = 17.3

The least distance at which one has to stand from a cliff to hear an echo is 17.3 m.

Answer 2

Given :-

• Distance = 2d (because echo is the reflected sound)
• Velocity = 346 m/s
• Time = 0.1 second (because any sound persists for 0.1 second in ear)

To find :-

• Find d

$\underline{\bf{\bigstar} \: \mathfrak{As \: we \: know \: that}}$

• $\boxed{\bf{Distance = Speed × Time}}$★

Solution :-

• Substituting the values :

:$\implies$2d = v × t

$~~~~~$:$\implies$2d = 346 × 0.1

$~~~~~~~~~~$:$\implies$2d = 34.6

$~~~~~~~~~~~~~~~$:$\implies$d = $\large{\sf{\frac{34.6}{2}}}$

$~~~~~~~~~~~~~~~~~~~~$:$\implies$${\sf{\dfrac{\cancel{34.6}}{\cancel{2}}}}$

$~~~~~~~~~~~~~~~~~~~~~~~~$:$\implies$$\large{\underline{\boxed{\pink{\frak{d~=~17.3}}}}}$★

$\large\dag$ Hence,

• The least distance at which one has to stand from a cliff to hear an echo is $\large\underline{\rm{17.3~m}}$ $\large{\bf\green{✓}}$