The phase difference between displacement and velocity of a particle in simple harmonic motion is

A particle is performing simple harmonic motion. Equation of its motion is $$x = 5\sin \left( {4t - {\pi \over 6}} \right),x$$ being the displacement from mean position. Velocity (in ms$$^{-1}$$) of the particle at the instant when its displacement is 3, will be

The function $$y = \log \omega t$$ can represent

Two spring of force constant $$k_1$$ and $$k_2$$ are configured as the figure given below

The angular frequency of this configuration is