What is the nucleus of an atom ?

Isotopes are atoms having

How the radius of the nucleus is estimated ? Write its relation to radius and atomic mass number. 

A nucleus disintegrates into two smaller parts, which have their velocities in the ratio $3: 2$. The ratio of their nuclear sizes will be $\left(\frac{x}{3}\right)^{\frac{1}{3}}$. The value of ' $x$ ' is :

Assume that the nuclear binding energy per nucleon $(B/A)$ versus mass number $(A)$ is as shown in the figure. Use this plot to choose the correct choice $(s)$ given below

$(A)$ Fusion of two nuclei with mass numbers lying in the range of $1 < A < 50$ will release energy

$(B)$ Fusion of two nuclei with mass numbers lying in the range of $51 < A < 100$ will release energy

$(C)$ Fission of a nucleus lying in the mass range of $100 < A < 200$ will release energy when broken into two equal fragments

$(D)$ Fission of a nucleus lying in the mass range of $200 < A < 260$ will release energy when broken into two equal fragments

$\pi $ mesons can be