A wheel is rotating at $600$ rpm about its axis of rotation. When the power is cut off, it comes to rest in half a minute. Its angular retardation expressed in $\text{rad}/\text{s}^2$ is (retardation is uniform)

A flywheel rotating about a fixed axis has a kinetic energy of $500$ joule, if its angular frequency is $5$ Hz, then calculate the moment of inertia of the wheel about the axis of rotation. ($\pi^2=10$)

Given below are two statements:
Statement I: Acceleration due to earth's gravity decreases as you go 'up' or 'down' from earth's surface.
Statement II: Acceleration due to earth's gravity is same at a height '$h$' and depths '$d$' from earth's surface, if $h = d$.
In the light of above statements, choose the most appropriate answer from the options given below.

Two rain drops of same radius '$r$' falling with same terminal velocity '$V$' merge and form bigger drop of radius '$R$'. The terminal velocity of big drop is