The temperature-entropy diagram of a reversible engine cycle is given in the figure. Its efficiency is

The function $${\sin ^2}\left( {\omega t} \right)$$ represents

The bob of a simple pendulum is a spherical hollow ball filled with water. A plugged hole near the bottom of the oscillating bob gets suddenly unplugged. During observation, till water is coming out, the time period of oscillation would

If a simple harmonic motion is represented by $${{{d^2}x} \over {d{t^2}}} + \alpha x = 0.$$ its time period is