The displacement of an elastic wave is given by the function : $y = 3\, sin\,\omega t + 4\, cos\,\omega t$ where $y$ is in $cm$ and $t$ is in $s$. The resultant amplitude is …… $cm$

A point source emits sound equally in all directions in a non-absorbing medium. Two points $P$ and $Q$ are at a distance of $9$ meters and $25$ meters respectively from the source. The ratio of the amplitudes of the waves at $P$ and $Q$ is

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 …. $m/s$

Two tuning forks $A$ and $B$ produce $8\,beats/s$ when sounded together. $A$ gas column $37.5\,cm$ long in a pipe closed at one end resonate to its fundamental mode with fork $A$ whereas a column of length $38.5\,cm$ of the same gas in a similar pipe is required for resonance with fork $B$. The frequencies of these two tuning forks, are

A plan wave of sound traveling in air is incident upon a plan surface of a liquid. The angle of incidence is $60^o$. The speed of sound in air is $300\ m/s$ and in the liquid it is $600\ m/s$. Assume Snell's law to be valid for sound waves