The mean free path of molecules of a gas, (radius r) is inversely proportional to

The oscillation of a body on a smooth horizontal surface is represented by the equation,
X = A cos$$\left( {\omega t} \right)$$
where X = displacement at time t
$$\omega $$ = frequency of oscillation
Which one of the following graphs shows correctly the variation a with t?
Here a = acceleration at time t
T = time period

If n₁, n₂ and n₃ are the fundamental frequencies of three segments into which a string is divided, then the original fundamental frequency n of the string is given by

The number of possible natural oscillations of air column in a pipe closed at one end length 85 cm whose frequencies lie below 1250 Hz are (Velocity of sound = 340 m s^$$-$$1)