A car $P$ approaching a crossing at a speed of $10\, m/s$ sounds a horn of frequency $700\, Hz$ when $40\, m$ in front of the crossing. Speed of sound in air is $340\, m/s$. Another car $Q$ is at rest on a road which is perpendicular to the road on which car $P$ is reaching the crossing (see figure). The driver of car $Q$ hears the sound of the horn of car $P$ when he is $30\, m$ in front of the crossing. The apparent frequency heard by the driver of car $Q$ is ...... $Hz$

A sound-source is moving in a circle and an observer is outside the circle at $O$ as shown in figure. If the frequencies as heard by the listener are $\nu _1, \nu _2$ and $\nu _3$ when the source is at $A, B$ and $C$ position, respectively, then

Two vibrating tuning forks produce waves given by ${y_1} = 4\sin 500\pi t$ and ${y_2} = 2\sin 506\pi t.$  Number of beats produced per minute is

A wave travelling in the $-ve\,\,z-$ direction having displacement along $x-$ direction as $1\,m,$ wavelength $\pi\, m$ and frequency at $\frac {1}{\pi }\,H_Z$ is represented by

Calculate the temperature at which the speed of sound will be two times its   ..... $K$ value at $0\,^oC$

A string with a mass density of $4\times10^{-3}\, kg/m$ is under tension of $360\, N$ and is fixed at both ends. One of its resonance frequencies is $375\, Hz$. The next higher resonance frequency is $450\, Hz$. The mass of the string is