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  • Created by: bob
  • Created on: 12-05-13 11:32

Newton's 1st Law of Motion

  • Every object remains in a state of constant velocity or remains stationary unless a resultant force acts upon it.
  • A resultant force is needed to produce an accleration.
  • If the resultant force is zero/no resultant force, the object will continue to move at a constant velocity/remain stationary.
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Newton's 2nd Law of Motion

  • Resultant force = mass x acceleration 
  • Acceleration and force are vectors
  • Resultant force is proportional to acceleration (and moves in the same direction)
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Newton's 3rd Law of Motion

  • Every action has an equal and opposite reaction 
  • If body A exerts a force on body B, then body B exerts an equal and opposite in direction reaction force of the same type on body A.
  • They are equal in magnitude, force type, and the time and line of action is the same.
  • They act in opposite directions and on different bodies.
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  • GRAVITY IS NOT A FORCE - it is acceleration
  • Weight = downwards force
  • Weight = mass x gravity
  • Magnitude of acceleration in freefall = gravitational field strength
  • Centre of gravity = the point where all the weight of an object is concentrated 
    (it is usually in the centre of the object)
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  • A free body diagram shows all the forces acting on one object (at the centre of gravity)
  • Weight always acts directly down
  • Normal contact force (reaction force) acts perpendicular to the surface (ground/slope)
  • Friction/drag forces always oppose motion. 
  • Vector diagram = closed polygon if the forces are in equilibrium (resultant force = 0)
  • Forces in equilibrium = constant velocity/stationary state (N1)
  • Draw vector arrows from tip to tail (resultant vector = tail of first --> tip of last)
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