Two (A and B) pendulums begin to swing simultaneously. The first pendulum (A) makes five oscillations when the other (B) makes three oscillations. The ratio of the lengths of pendulum $A$ to that of $B$ is

A particle performs S.H.M. with amplitude 'A'. The speed of the particle is $\left(\frac{1}{3}\right)^{\text {rd }}$ of the maximum speed when its displacement from the mean position is

A particle vibrating simple harmonically has an acceleration of $16 \mathrm{~cm} / \mathrm{s}^2$, when it is at a distance of 4 cm from the mean position. Its periodic time is

The average velocity of a particle performing S.H.M. in one complete vibration is ( $\mathrm{A}=$ amplitude of S.H.M., $\omega=$ angular velocity)