The beats are produced when there is a superposition of two sound waves which will have

In a pipe closed at one end, air column is vibrating in the fourth overtone so the vibrating air column has '$x$' nodes and '$y$' antinodes. The values of $x$ and $y$ are respectively

Two sounding waves send waves at certain temperature in air of wavelength 50 cm and 50.5 cm repectively. The frequency of sources differ by 6 Hz. The velocity of sound in air at same temperature is

Three point charges +q, +2q and +Q are placed at the vertices of an equilateral triangle. If the potential energy of the system of three charges is zero, the value of Q in terms of q is