The gravitational force between H-atom and another particle of mass m will be given by Newton's law \(F=\frac{GMm}{r^2},\) where r is
in km and

When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom:
 

Tritium is an isotope of hydrogen whose nucleus triton contains 2 neutrons and 1 proton. Free neutrons decay into $\mathrm{p}+\overline{\mathrm{e}}+\overline{\mathrm{\nu }}$. If one of the neutrons in Triton decays, it would transform into He³ nucleus. This does not happen. This is because;
 

M_x and M_y denote the atomic masses of the parent and the daughter nuclei respectively in radioactive decay. The Q-value for a ${\mathrm{\beta }}^{-}$ decay is Q₁ and that for a ${\mathrm{\beta }}^{+}$ decay is Q₂. If ${\mathrm{m}}_{\mathrm{e}}$ denotes the mass of an electron, then which of the following statements is correct?

1. ${\mathrm{Q}}_1=({\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}) {\mathrm{c}}^2 \mathrm{and} {\mathrm{Q}}_2=[{\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}-2{\mathrm{m}}_{\mathrm{e}}]{\mathrm{c}}^2$

2. ${\mathrm{Q}}_1=({\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}) {\mathrm{c}}^2 \mathrm{and} {\mathrm{Q}}_2=({\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}) {\mathrm{c}}^2$

3. ${\mathrm{Q}}_1=({\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}-2{\mathrm{m}}_{\mathrm{e}}) {\mathrm{c}}^2 \mathrm{and} {\mathrm{Q}}_2=({\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}+2{\mathrm{m}}_{\mathrm{e}}) {\mathrm{c}}^2$

4. ${\mathrm{Q}}_1=({\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}+2{\mathrm{m}}_{\mathrm{e}}) {\mathrm{c}}^2 \mathrm{and} {\mathrm{Q}}_2=({\mathrm{M}}_{\mathrm{x}}-{\mathrm{M}}_{\mathrm{y}}+2{\mathrm{m}}_{\mathrm{e}}){\mathrm{c}}^2$

In a nuclear reactor, moderators slow down the neutrons which come out in a fission process. The moderator used have light nuclei. Heavy nuclei will not serve the purpose, because:

Fusion processes, like combining two deuterons to form a \(\mathrm{He}\)-nucleus are impossible at ordinary temperatures and pressure. The reasons for this can be traced to the fact:

1. (a, c)
2. (a, d)
3. (b, d)
4. (a, b)