At what angle should an unpolarised beam be incident on a crystal of refractive index $\mu = \sqrt{3}$,so that the reflected beam is completely polarised (in $^o$)?

It takes $10$ minutes to cool a liquid from $61^oC$ to $59^oC$. If room temperature is $30^oC$,then the time taken in cooling from $51^oC$ to $49^oC$ is ....... $\min$.

$A$ body moving with uniform acceleration travels a distance of $25 \ m$ in the fourth second and $37 \ m$ in the sixth second. The distance covered by the body in the next two seconds is (in $m$)

If $\alpha$ is a non-real root of $x^6=1$,then $\frac{\alpha^5+\alpha^3+\alpha+1}{\alpha^2+1}$ is equal to

Two discs of moments of inertia $I_1$ and $I_2$ about their respective axes (normal to the disc and passing through the centre),and rotating with angular speed $\omega_1$ and $\omega_2$ are brought into contact face to face with their axes of rotation coincident. What is the loss in kinetic energy of the system in the process?

The reaction $A \xrightarrow{k}$ Product is zero order,while the reaction $B \xrightarrow{k}$ Product is a first order reaction. For what initial concentration of $A$ are the half-lives of the two reactions equal?