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These two forces, which are very different, are often linked together by physical scientists because they both operate within the nucleus. The strong force prevents the positively charged protons in the nucleus from flying apart; it is stronger than the repulsion, but only acts at short distances. The weak force is responsible for a particular decay mode of nuclei, beta decay, which involves the emission or capture of electrons or positrons. At high energies, such as inside particle accelerators, the weak force becomes much more important.
The strong force is due to gluon exchange between the quarks that the protons and neutrons in the nucleus contain. This exchange only occurs within the protons and neutron, however, and does not bind the nucleus together. This is done by the ‘leakage’ from the gluon exchange in the form of the exchange of another particle, the pion, between the protons and neutrons themselves. The strong force is very different from the other three forces in that it grows stronger with distance, like stretching a piece of elastic. Thus, if we attempt to separate two quarks, all we do by pulling them apart is increase the attractive force and the interaction energy between them. If they are pulled apart until the interaction energy is equivalent to the mass of two new quarks, then two new quarks will immediately be formed, and we will have two pairs rather than the one that we started with. This property of the strong force leads to confinement of quarks, which means that it is impossible to find a single quark: they only come in pairs or threes.
The weak force involves other exchange particles, the Z and W bosons. They are can interact with the orbiting electrons and the protons and neutrons within the nucleus. This force has the property of not conserving parity, or mirror symmetry, in its interactions. JJ
See also four forces; parity. |
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