Net force between two nucleons 1fm apart is F1 if both are protons ,F2 if both are neutrons ,F3 if one is neutron and other is proton. Explain why F1

Nuclear forces are the strong forces of attraction which hold together the nucleons (neutrons and protons) in the tiny nucleus of an atom, inspite of strong electrostatic forces of repulsion between protons. Nuclear forces act between a pair of neutrons, a pair of protons and also between a neutron, proton pair with the same strength. This shows that nuclear forces are independent of charge. 
The attractive nuclear force is the same for any pair of nucleons. Thus F1 = F3 when there are no electrostatic forces, but F2 = attractive nuclear force - repulsive electrostatic force