A2

• newton's first law of motion


  an object continues in uniform motion in a straight line or at rest unless a resultant external force acts
• newton's second law of motion

  a resultant force causes an acceleration
• tension


  the force arising when a body is being stretched or compressed
• normal contact force


  the force between two touching bodies that is perpendicular to the touching surface
• hooke's law


  the tension in a spring is proportional to the extension or compression
• newton's third law of motion


  for every action there is an equal and opposite reaction
• dynamic friction


  a force opposing motion when a body moves
• static friction


  a force opposing the tendency to motion when a body is at rest
• coefficient of static friction

  the ration of the maximum force of friction between two bodies to the normal contact force when an object is at rest
• coefficient of dynamic friction


  the ratio of the force of friction to the normal contact force on a body that is sliding along a surface
• drag force


  the force acting on an object in a fluid because the object is displacing some of the fluid
• Archimedes' principle


  when a body is wholly or partly immersed in a fluid it experiences an upward boyant force which is equal to the weight of the fluid displaced
• time period


  the time it takes for an orbiting objct to make ome complete orbit
• frequency


  the number of complete orbits made in one second
• centripetal force


  the force, directed towards the center of a circular orbit, necessary for a body to move in orbit
• centripetal acceleration


  the rate of chnage of velocity of a body in orbit
• momentum


  how hard it is to stop an object that is in motion
• impulse


  the product of force and time

  change in momentum
• conservation of momentum


  in any closed system the momentum is constant
• closed system


  where there are no external forces acting
• elastic


  momentum and kinetic energy are conserved
• inelastic 


  momentum is conserved, kinetic energy can be lose due to resistive
• collision


  any event in which two or more bodies exert forces on each other for a relatively short time
• explosion


  an internal impulse acts in order to propel the parts of a system into a variety of direcion
• elastic collision


  there is no loss of kinetic energy in the collision
• inelastic collision


  part of the kinetic energy is transferred to some other store of energy in the collision