A solid cylinder rolls down on an inclined plane of height $h$ and inclination $\theta$. The speed of the cylinder at the bottom is

Three particles of each mass $m$ are kept at the three vertices of an equilateral triangle of side $l$. The moment of inertia of a system of the particles about any side of the triangle is

In a spring block system as shown in figure. If the spring constant $k=9 \pi^2 \mathrm{Nm}^{-1}$, then the time period of oscillation is

A body is executing simple harmonic motion. At a displacement $x$ its potential energy is $E_1$ and at a displacement $y$ its potential energy is $E_2$. The potential energy $E$ at a displacement $(x+y)$ is