The speeds of the seven molecules are 1, 3, 5, 7, 2, 4 and 6 km/s respectively. The ratio of their r.m.s. velocity and average velocity will be

Two simple pendulums of lengths $L_1$ and $L_2$ have periodic time $T_1$ and $T_2$ respectively $(T_1 > T_2)$. The time period of the pendulum of length $(L_1-L_2)$ is
$[(L_1-L_2) > 60\text{ cm}]$

For a particle executing S.H.M., its potential energy is 8 times its kinetic energy at a certain displacement '$x$' from the mean position. If '$A$' is the amplitude of S.H.M., the value of '$x$' is

A particle executing simple harmonic motion starts from mean position with amplitude '$A$' and periodic time '$T$'. At what displacement is its speed one-fourth of the maximum speed?