My (high school) physics teacher was telling us about quarks and how the colour force between quarks is responsible for the strong nuclear force among baryons. He also claimed that unlike other forces, this force became stronger over a distance which is why it requires alot of energy to separate quarks. I do not understand how it is possible to have a force that becomes stronger as distance increases. If this is so, how is it possible to to have protons and neutrons not bound to the nucleus? Wouldnt it be impossible to ever supply enough energy to have free baryons? Did my teacher incorrectly describe the distribution of the strong nuclear force?