Assertion If electrons in an atom were stationary, then they would fall into the nucleus.

Reason Electrostatic force of attraction acts between negatively charged electrons and positive nucleus.

Assertion Radioactive nuclei emits $$\beta^{-}$$-particles.

Reason Electrons exist inside the nucleus.

A nuclear explosive is designed to deliver $$1 \mathrm{~MW}$$ power in the form of heat energy. If the explosion is designed with nuclear fuel consisting of $$U^{235}$$ to run a reactor at this power level for one year, then the amount of fuel needed is (Given energy per fission is $$200 \mathrm{~MeV}$$)

Assertion : A beam of charged particles is employed in the treatment of cancer.

Reason : Charged particles on passing through a material medium lose their energy by causing ionization of the atoms along their path.