In an experiment to measure the speed of sound in air, a boy stands $40 \mathrm{m}$ away from a wall and bangs two pieces of wood together. At the instant he hears the echo, he bangs them together again. He does this activity $50$ times. The time taken for $50$ bangs is $12 \mathrm{s}$. Which calculation gives the speed of sound in air?

A student performed an experiment as shown in the figure. 

What happened when air was pumped out of the jar and the electric bell rang ?

A tuning fork sends sound waves in air. If the temperature of air increases, which of the following parameters will change?

Read the given statements and select the correct option.
Statement $1$: Sound would travel faster on a hot summer day than on a cold winter day.

Statement $2$: Velocity of sound depends on temperature.

A man fires a gun $150 \mathrm{m}$ from a cliff. A second man who is standing $300 \mathrm{m}$ farther away from the cliff hears the gun $1$ second after he sees the flash. The second man will hear the echo from the cliff

A dog barks in a park and hears its echo after $0.5$ seconds. The sound of its bark got reflected by a nearby building. The sound of speed in air is $346 \mathrm{m} {\mathrm{s}}^{-1}$. The distance between the dog and the building is

The picture shows a xylophone. $\mathrm{A}, \mathrm{B}, \mathrm{C}$ and $\mathrm{D}$ are the rods in it. Which of the following rods has high pitch of the sound and which has low frequency of vibrations?

A student sets up a slinky $\mathrm{PQ}$ on a smooth table top in the manner as shown in figure. How can he produce transverse waves in the slinky by moving its free end $\mathrm{Q}$ ?