A train standing at the outer signal of a railway station blows a whistle of frequency $400\, Hz$ in still air. What is the frequency of the whistle for a platform observer when the train recedes from the platform with a speed of $10\, m/s$ ...... $Hz$ . (Speed of sound $= 340\, m/s$)

The figure represents the instantaneous picture of a transverse harmonic wave traveling along the negative $x$-axis. Choose the correct alternative $(s)$ related to the movement of the nine points shown in the figure.  The stationary points is/are

A transverse wave is passing through a stretched string with a speed of $20\  m/s$ . The tension in the string is $20\ N$ . At a certain point $P$ on the string, it is observed that energy is being transferred at a rate of $40\ mW$ at a given instant. Find the speed of point $P$

An engine approaches a hill with a constant speed. When it is at a distance of $0.9 km$ it blows a whistle, whose echo is heard by the driver after $5$ sec. If speed of sound in air is $330 m/s$, the speed of engine is .... $m/s$

A transverse wave is described by the equation $y = {y_0}\,\sin \,2\pi \,\left[ {ft - \frac{x}{\lambda }} \right]$ . The maximum particle velocity is equal to four times the wave velocity if

A transverse harmonic wave on a string is described by $y = 3\sin \left( {36t + 0.018x + \frac{\pi }{4}} \right)$ where $x$ and $y$ are in $cm$ and $t$ in $s$. The least distance between two successive crests in the wave is .... $m$