$A$ light wave enters from medium $1$ to medium $2$. Its velocity in the $2^{\text{nd}}$ medium is double that in the $1^{\text{st}}$ medium. For total internal reflection,the angle of incidence must be greater than ....... $^{\circ}$.

The electric current $i$ in the circuit shown is (in $A$)

$A$ small sphere oscillates simple harmonically in a watch glass whose radius of curvature is $1.6 \ m$. The period of oscillation of the sphere in seconds is (acceleration due to gravity,$g = 10 \ m/s^2$). (in $pi$)

$A$ circular disc is rolling on a horizontal plane. Its total kinetic energy is $300 \ J$. What is its translational kinetic energy?

At a certain instant, a stationary transverse wave is found to have maximum kinetic energy. The appearance of the string at that instant is: