• There are many different forces like contact force, gravity force, inertia force, wind force, fluid pressure force, static force, thermal force, centrifugal , frictional force, pushing force, pulling force, seismic force, snow force, normal force, tangential force etc.
  • Without a force no action like dancing, cycling, playing sports. Even a stationary object is under the action of its weight.
  • The unit of force is Newton (N).1 Newton = accelerating an object of mass of 1 kg  at 1 m/s21 pound force =4.448 N
  • 1 kg force= 9.81 N
  • A force has both magnitude and direction and hence is a vector quantity like velocity/acceleration/displacement.
  • A vector is represented by a line of certain length and an arrow placed at one end. The length of the line represents the magnitude of the force and the  arrow used to show the direction.
  • A force is an effect which does the followings
  •  Makes a stationary body to move
  •  Accelerate a moving body
  •  Retard a moving body
  •  Stop motion
  •  Change direction
  •  Cause deformation
  •  Remove deformation
  • All or any one or two forces which act on objects.
  • When forces act in pairs, these are either balanced or unbalanced.


  • Balanced forces do not cause change in position or deformation or motion.
  • They are equal in magnitude and opposite in direction and there is no net force.


  • An unbalanced force always causes a change in motion or position or deformation.
  • When unbalanced forces act in opposite directions you can find the net force.

Net force magnitude will be the difference between the two forces.

  • Direction of the net force will be the direction of the largest force.
  • If forces are balanced the object doesn’t move.
  • If forces are unbalanced the object will do one of  the following things:
  •  Begin to move
  •  Stop moving
  •  Changes direction
  •  Speeds up
  •   Slows down