Final answer:
The Coulomb force between protons in the nucleus is repulsive, but the strong nuclear force overcomes this repulsion and holds the nucleus together.
Step-by-step explanation:
The Coulomb force, which is the electromagnetic force between two charged particles, has a repulsive nature when the charges are of the same sign. In the atomic nucleus, the protons have positive charges, so they repel each other due to the Coulomb force.
However, the nucleus is held together by the strong nuclear force, which is stronger than the Coulomb force at very short distances. This force is attractive and acts between all nucleons in the nucleus, including protons and neutrons.
Since the strong nuclear force is stronger than the Coulomb force, it overcomes the repulsion between protons and helps to keep the nucleus stable.
As a result, it is harder to separate a proton from the nucleus than a neutron, as the strong nuclear force plays a significant role in holding protons together despite their repulsion.