Non-contact force

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A non-contact force is a force applied to an object by another body that is not in direct contact with it. The most familiar example of a non-contact force is weight. In contrast a contact force is a force applied to a body by another body that is in contact with it. However it is to be noted that the origin of all contact forces (such as, for example, friction) can be traced to non-contact forces.

All four known fundamental interactions are non-contact forces:

  • Gravity, the force of attraction that exists among all bodies that have mass. The force exerted on each body by the other through weight is proportional to the mass of the first body times the mass of the second body divided by the square of the distance between them.
  • Strong nuclear force: Unlike gravity and electromagnetism, the strong nuclear force is a short distance force that takes place between fundamental particles within a nucleus. It is charge independent and acts equally between a proton and a proton, a neutron and a neutron, and a proton and a neutron. The strong nuclear force is the strongest force in nature; however, its range is small (acting only over distances of the order of 10−15 m). The strong nuclear force mediates both nuclear fission and fusion reactions.

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