An echo is heard after $0.8 \, s$,when a person fires a cracker $132.8 \, m$ from a high building. Calculate the speed of sound.

In $SONAR$, we use

$A$ stretched wire $0.5\, m$ long is made to vibrate in two different modes as shown in diagrams $(A)$ and $(B)$ given below:
$(i)$ If the wavelength of the wave produced in mode $(A)$ is $1\, m$,what is the wavelength of the wave produced in mode $(B)$ of the following diagram?
$(ii)$ In which case is the note produced louder? Give a reason for your answer.
$(iii)$ In which case is the pitch of the note produced higher? Give a reason for your answer.

Sound travels in air if

$A$ key of a mechanical piano is struck gently and then struck again but much harder this time. In the second case,

State whether the following statement is true or false:
Sound travels faster at a higher temperature than at a lower temperature.