Forces in Nature

• what is a force?


  a push or pull
• what are the four fundamental forces?

  gravity, electromagnetism, weak nuclear, strong nuclear
• gravity


  force of attraction between all objects
• electromagnetism

  the force of attraction or repulsion caused by electric charges
• weak nuclear


  the force responsible for interactions involving particles (eg. protons & neutrons). can be either attraction or repulsion
• strong nuclear

  the force that holds protons and neutrons together in the nucleus of an atom. can either be attraction or repulsion
• common forces

  normal force, friction, tension, applied force
• normal force


  a force perpendicular to the surface of an object in contact
• friction


  a force between objects in contact that acts parallel to the surface and in the opposing direction of motion
• tension


  the pulling force exerted by strings, ropes, fibres, and cables
• applied force


  general name for any contact force
• system diagram


  a drawing of all objects involved in a situation
• free body diagram


  drawing where only the object being analyzed is drawn, with arrows showing the forces acting on the object