Which of the following isotopes is normally fissionable ?
$_{92}{U^{238}}$
$_{93}N{p^{239}}$
$_{92}{U^{235}}$
$_{2}{He^{4}}$
A positron is emitted from ${ }^{23} \mathrm{Na}_{11}$. The ratio of the atomic mass and atomic number of the resulting nuclide is
Assertion : The binding energy per nucleon, for nuclei with atomic mass number $A > 100$, decreases with $A$.
Reason : The nuclear forces are weak for heavier nuclei.
The nuclei ${ }_{6} C^{13}$ and ${ }_{7} N^{14}$ can be described as
As compared $^{12}C$ atom, $^{14}C$ atom has
An unstable heavy nucleus at rest breaks into two nuclei which move away with velocities in the ratio of $8:27$. The ratio of the radii of the nuclei (assumed to be spherical ) is