The density (in $kg m^{-3}$) of nuclear matter is of the order of

Give one example each of central force and non-central force.

The force between a proton and a proton in a nucleus is .......

$A$ nucleus splits into two parts. If the ratio of their velocities is $8 : 1$, what is the ratio of their radii?

How many neutrons are more than protons in the ${ }_{92}^{235} U$ nucleus?

$(a)$ Two stable isotopes of lithium $_{3}^{6} Li$ and $_{3}^{7} Li$ have respective abundances of $7.5 \%$ and $92.5 \%$. These isotopes have masses $6.01512 \; u$ and $7.01600 \; u$,respectively. Find the atomic mass of lithium.
$(b)$ Boron has two stable isotopes,$_{5}^{10} B$ and $_{5}^{11} B$. Their respective masses are $10.01294 \; u$ and $11.00931 \; u$,and the atomic mass of boron is $10.811 \; u$. Find the abundances of $_{5}^{10} B$ and $_{5}^{11} B$.