A coil of '$$n$$' turns and radius '$$R$$' carries a current '$$I$$'. It is unwound and rewound again to make another coil of radius $$\left(\frac{\mathrm{R}}{3}\right)$$, current remaining the same. The ratio of magnetic moment of the new coil to that of original coil is

An ink mark is made on a piece of paper on which a glass slab of thickness '$$t$$' is placed. The ink mark appears to be raised up through a distance '$$x$$' when viewed at nearly normal incidence. If the refractive index of the material of glass slab is '$$\mu$$' then the thickness of glass slab is given by

A spherical metal ball of radius '$$r$$' falls through viscous liquid with velocity '$$\mathrm{V}$$'. Another metal ball of same material but of radius $$\left(\frac{r}{3}\right)$$ falls through same liquid, then its terminal velocity will be

A body of mass '$$\mathrm{m}$$' attached at the end of a string is just completing the loop in a vertical circle. The apparent weight of the body at the lowest point in its path is ( $$\mathrm{g}$$ = gravitational acceleration)