Assume that a neutron breaks into a proton and an electron. The energy released during this process is: ............ $MeV$ (mass of neutron $= 1.6725 \times 10^{-27} \ kg$,mass of proton $= 1.6725 \times 10^{-27} \ kg$,mass of electron $= 9 \times 10^{-31} \ kg$).

In the nuclear reaction ${ }_{7}^{14} N + X \rightarrow { }_{6}^{14} C + { }_{1}^{1} H$,the $X$ will be

Which stable nucleus has a radius that is half that of $Fe^{56}$?

Assertion: Isobars are the elements having same mass number but different atomic number.
Reason: Neutrons and protons are present inside the nucleus.

Which is the correct unit for measuring nuclear radii?

It is now believed that protons and neutrons (which constitute nuclei of ordinary matter) are themselves built out of more elementary units called quarks. $A$ proton and a neutron consist of three quarks each. Two types of quarks,the so-called 'up' quark (denoted by $u$) of charge $+(2/3)e$,and the 'down' quark (denoted by $d$) of charge $-(1/3)e$ together with electrons build up ordinary matter. Suggest a possible quark composition of a proton and neutron.