Fast neutrons can easily be slowed down by

$A$ ${ }_{92} U^{235}$ nucleus absorbs a neutron and disintegrates into ${ }_{54} X e^{139}$,${ }_{38} S r^{94}$,and $X$. What will be the product $X$?

Which is more destructive: an atomic bomb or a hydrogen bomb?

The energy released per fission of a nucleus of ${}^{240}X$ is $200 \ MeV$. The energy released if all the atoms in $120 \ g$ of pure ${}^{240}X$ undergo fission is $........ \times 10^{25} \ MeV$. (Given $N_A = 6 \times 10^{23}$)

The energy released per fission of uranium-$235$ is about $200 \, MeV$. $A$ reactor using $U-235$ as fuel is producing $1000 \, kW$ power. The number of $U-235$ nuclei undergoing fission per second is approximately:

If $200 \text{ MeV}$ of energy is released in the fission of one nucleus of ${ }_{92}^{236} U$,the number of nuclei that must undergo fission to release an energy of $1000 \text{ J}$ is