Answer 1

Let the length of the aluminium rod be d.

Speed of sound wave in aluminium at 25°C, v_Al = 6420 ms^-1

Therefore, time taken by the sound wave to reach the other end,

`t_(Al)=d/"v"_(Al)=d/6420`

Speed of sound wave in air at 25°C, v_Air = 346 ms^-1

Therefore, time taken by sound wave to reach the other end,

`t_(Air)=d/"v"_(Air)=d/346`

The ratio of time taken by the sound wave in air and aluminium:-

`t_(Air)/t_(Al)=(d/346)/(d/6420)=6420/346=18.55`