A transverse wave is travelling along a stretched string from right to left. The figure shown represents the shape of the string at a given instant. At this instant
the particles at $A, B$ and $H$ have downward velocity
the particles at $D, E$ and $F$ have downward velocity
the particles at $C, E$ and $G$ have zero velocity
the particles at $A$ and $F$ have maximum velocity
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 ?
The ratio of the velocity of sound in hydrogen $(\gamma = 7/5)$ to that in helium $(\gamma = 5/3)$ at the same temperature is
A tuning of fork of frequency $392\, Hz$, resonates with $50\, cm$ length of a string under tension $(T)$. If length of the string is decreased by $2\%$, keeping the tension constant, the number of beats heard when the string and the tuning fork made to vibrate simultaneously is
The stationary wave $y = 2a{\mkern 1mu} \,\,sin\,\,{\mkern 1mu} kx{\mkern 1mu} \,\,cos{\mkern 1mu} \,\omega t$ in a stretched string is the result of superposition of $y_1 = a\,sin\,(kx -\omega t)$ and
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 ..... $Hz$