$A$ pair of tuning forks produces $2$ beats in a time interval of $0.4 \ s$. The beat frequency is .... $Hz$.

$A$ source of frequency $\nu$ gives $5$ beats/second when sounded with a source of frequency $200 \;Hz$. The second harmonic of frequency $2\nu$ of the source gives $10$ beats/second when sounded with a source of frequency $420 \;Hz$. The value of $\nu$ is .... $Hz$.

Each of the two strings of length $51.6 \, cm$ and $49.1 \, cm$ are tensioned separately by $20 \, N$ force. The mass per unit length of both strings is the same and equal to $1 \, g/m$. When both strings vibrate simultaneously,the number of beats is:

$A$ tuning fork and an air column whose temperature is $51^{\circ} C$ produce $4$ beats in one second,when sounded together. When the temperature of the air column decreases,the number of beats per second decreases. When the temperature is $16^{\circ} C$,only one beat per second is produced. The frequency of the tuning fork is ........... $Hz$.

$A$ source of unknown frequency gives $4\, \text{beats/s}$ when sounded with a source of known frequency $250\, \text{Hz}.$ The second harmonic of the source of unknown frequency gives $5\, \text{beats/s}$ when sounded with a source of frequency $513\, \text{Hz}.$ The unknown frequency is .... $\text{Hz}$

When two tuning forks are sounded together,$6$ beats per second are heard. One of the forks is in unison with $0.70 \ m$ length of a sonometer wire and another fork is in unison with $0.69 \ m$ length of the same sonometer wire. The frequencies of the two tuning forks are: