A particle of mass ' m ' is executing S.H.M. about the origin on $x$-axis with frequency $\sqrt{\frac{\mathrm{ka}}{\pi \mathrm{m}}}$, where ' $k$ ' is a constant and ' $a$ ' is the amplitude of S.H.M. If ' x ' is a displacement of a particle, at time ' $t$ ', potential energy of the particle will be

A pendulum is performing simple harmonic motion. The acceleration of the bob is $20 \mathrm{~cm} \mathrm{~s}^{-2}$ at a distance of 5 cm from mean position. The time period of oscillation is

Two particles execute S.H.M. of same amplitude and frequency along the same straight line path. They pass each other when going in opposite directions, each time their displacement is half the amplitude. The phase difference between them is $\left(\sin 30^{\circ}=0 \cdot 5\right)$