Three spheres, each of mass ' $m$ ' and radius ' $r$ ' are placed as shown in figure. Consider an axis $\mathrm{YY}^{\prime}$, which is touching two spheres and passing through the diameter of third sphere. The moment of inertia of the system consisting of these three spheres about $\mathrm{YY}^{\prime}$ axis is

A wheel initially at rest, begins to rotate about its axis with constant angular acceleration. If it rotates through an angle $\theta_1$ in first 2 s and a further angle $\theta_2$ in the next 2 s , the ratio $\theta_1: \theta_2$ is

A solid sphere rolling without friction on a horizontal surface with a constant speed of $2 \mathrm{~m} / \mathrm{s}$, rolls up on an inclined ramp which is inclined at $30^{\circ}$. The maximum distance travelled by the sphere on the inclined ramp is (acceleration due to gravity $\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2, \sin 30^{\circ}=\frac{1}{2}$ )

A disc of mass ' $m$ ' and radius ' $r$ ' rolls down an inclined plane of height ' $h$ '. When it reaches the bottom of the plane, its rotational kinetic energy is ( $\mathrm{g}=$ acceleration due to gravity)