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2012-12-14 17:32:52

Physics: Forces and the Laws of Motion
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  1. Force:
    an action exerted on an object which may change the object’s state of rest or motion. SI unit is Newton.
  2. A Newton
     is the amount of force that, when acting on a 1 kg mass, produces an acceleration of 1 .
  3. Free-body diagram
    includes only the forces that act on the object.
  4. Newton’s First Law of Motion:
    An object at rest remains at rest, and an object in motion continues in motion with constant velocity in a straight line unless the object experiences a net external force.
  5. Inertia
    is the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction.
  6. net force.
    The sum of forces acting on an object
  7. Equilibrium:
     the state in which the net force on an object is zero.  The object may be at rest or moving at constant velocity.
  8. Newton’s Second Law of Motion:
    The acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to the object’s mass.  F = ma
  9. Newton’s Third Law of Motion:
    If two objects interact, the magnitude of the force exerted on object 1 by object 2 is equal to the magnitude of the force simultaneously exerted on object 2 by object 1, and these two forces are opposite in direction. Note: action and reaction forces each act on different objects.
  10. Weight:
    a measure of the gravitational force exerted on an object; its value can change with the location of the object in the universe.
  11. Normal force:
    a force that acts on a surface in a direction perpendicular to the surface
  12. Friction
    is a resistive force that acts in a direction opposite to the direction of the relative motion of two contacting surfaces.
  13. Static friction:
    the force that resists the initiation of sliding motion between two surfaces which are in contact and at rest
  14. Kinetic friction:
    the force that opposes the movement of two surfaces which are in contact and are sliding over each other
  15. Force of friction
    is proportional to the normal force. is always parallel to the surface of contact.
  16. Force of kinetic friction
    is always opposite the direction of motion.
  17. Coefficient of friction:
    the ratio of the magnitude of the force of friction between two objects in contact to the magnitude of the normal force with which the objects press against each other.
  18. Terminal speed:
    maximum downward speed when falling through a gas or liquid.
  19. Four fundamental forces:
    gravitational, strong and weak nuclear, and electromagnetic.