In a nuclear fusion process,the mass defect is $0.05\%$. How much energy will be released from $1 \, kg$ of mass?

The nucleus $_{92}U^{234}$ splits exactly in half in a fission reaction in which two neutrons are released. The resultant nuclei are

Carbon-$11$ decays to boron-$11$ according to the following formula:
${ }_{6}^{11} C \rightarrow{ }_{5}^{11} B +e^{+}+ v _{e}+0.96 \,MeV$
Assume that,positrons $\left(e^{+}\right)$ produced in the decay combine with free electrons in the atmosphere and annihilate each other almost immediately. Also,assume that the neutrinos $\left(v _{e}\right)$ are massless and do not interact with the environment. At $t=0$,we have $1 \,\mu g$ of ${ }_{6}^{11} C$. If the half-life of the decay process is $t _{0}$,the net energy produced between time $t=0$ and $t=2 t _{0}$ will be nearly ........... $MeV$.

Suppose a ${ }_{88}^{226} Ra$ nucleus at rest and in the ground state undergoes $\alpha$-decay to a ${ }_{86}^{222} Rn$ nucleus in its excited state. The kinetic energy of the emitted $\alpha$ particle is found to be $4.44 \text{ MeV}$. The ${ }_{86}^{222} Rn$ nucleus then goes to its ground state by $\gamma$-decay. The energy of the emitted $\gamma$-photon is . . . . . . . $\text{keV}$.
[Given: atomic mass of ${ }_{88}^{226} Ra = 226.005 \text{ u}$,atomic mass of ${ }_{86}^{222} Rn = 222.000 \text{ u}$,atomic mass of $\alpha$ particle $= 4.000 \text{ u}$,$1 \text{ u} = 931 \text{ MeV}/c^2$]

The energy released in a typical nuclear fusion reaction is approximately..........$MeV$.

Explain an example in which heat transfer is necessary.