$A$ drop of liquid of diameter $2.8\, mm$ breaks up into $125$ identical drops. The change in energy is nearly ......... $ergs$ (Surface tension $= 75\, dyne/cm$)

The velocities of three particles of masses $20 \ g$,$30 \ g$ and $50 \ g$ are $10 \hat{i}$,$10 \hat{j}$ and $10 \hat{k}$,respectively. The velocity of the centre of mass of the three particles is

The equation of the sphere passing through the points $(1,0,0)$, $(0,1,0)$, and $(1,1,1)$ and having the smallest radius is:

In a nuclide,one $a.m.u.$ of mass is dissipated into energy to bind its nucleons. The energy equivalent of this mass is

The length of the common chord of the circles of radii $15$ and $20$,whose centers are $25$ units of distance apart,is

Smoke is an example of