Explain about rocket launch on the basis of conservation of momentum.

A toy car of mass $250 \mathrm{g}$ is moving with a velocity of $5 {\mathrm{ms}}^{-1}$, its momentum is _____ ${\mathrm{kgms}}^{-1}$.

A body of mass $50 \mathrm{kg}$ has a momentum of $250 {\mathrm{kgms}}^{-1}$, its velocity is _____${\mathrm{ms}}^{-1}$.

The rockets work on the principle of conservation of:

The momentum of an object is given by the formula : $momentum=mass\times x$. Here $x$ is _____.

Conservation of linear momentum means that initial momentum is _____ (not equal / equal) to the final momentum.