A whistle revolves in a circle with an angular speed of $20\, rad/s$ using a string of length $50\, cm$. If the frequency of sound from the whistle is $385\, Hz$, then what is the minimum frequency heard by an observer, which is far away from the centre in the same plane  ..... $Hz$ (speed of sound is $340\, m/s$)

The speed of sound in oxygen $(O_2)$ at a certain temperature is $460\, ms^{-1}$. The speed of sound in helium $(He)$ at the same temperature will be ............. $\mathrm{m/s}$  (assume both gases to be ideal)

When a wave travels in a medium, the particle displacement is given by : $y = asin\, 2 \pi \,(bt -cx)$, where $a, b$ and $c$ are constants. The maximum particle velocity will  be twice the wave velocity if

A train is moving towards a stationary observer. Which of the following curve best represents the frequency received by observer $f$ as a function of time ?

A stretched string is divided into three segments of lengths $50\,cm,\,\,40\,cm$ and $10\,cm$ with the help of bridges. Their vibrations will have frequencies in the ratio

Two cars $A$ and $B$ are moving in the same direction with speeds $36\, km/hr$ and $54 \,km/hr$ respectively. Car $B$ is ahead of $A$. If $A$ sounds horn of frequency  $1000\, Hz$ and the speed of sound in air is $340\, m/s$, the frequency of sound  received by the driver of car $B$ is ..... $Hz$