• A push or pull exerted by an object on another is a force.
  • Force arises due to the interaction between at least two objects.
  • Force has both Magnitude and Direction
  • Force applied on an object in the same direction add to one another.

  • If the two forces act in the opposite direction on an object, the net force acting on it is the difference between the two forces.

  • In general, more than one force may be acting on an object at any given point.
  • However, a force acting on an object is always the mean net force acting on it.

Two friends pushing a heavy load (a) in the same direction and (b) in the opposite direction


  • A Force can Change the State of Motion


  • A change in the speed of an object or the direction of its motion or both implies a change in its state of motion.


  • Force acting on an object may bring a change in its state of motion or a change in its shape.


Ex: A rubber band suspended from a hook/nail fixed on a wall.

By hanging a weight or by pulling its free end.

Types of Forces:

Contact Forces: The forces act on a body when the source of force is in actual contact with the body.

  • (i)  Muscular Force: The force exerted by the muscles of the body.

  • (ii)  Mechanical Force: The force produced by a machine.

  • (iii)  Frictional Force: The force that opposes the motion of an object.

Non-Contact Forces: Forces which do not involve physical contact between two bodies on which they act.

  • (i)  Magnetic Force: A magnet exerts a non-contact force on objects made of iron, steel, cobalt or nickel.

  • (ii)  Electrostatic Force: The force which result due to repulsion of similar charges or attraction of opposite charges.

  • (iii)  Gravitational Forces: The force that exists between any two masses because of their mass.


  • Thrust: The force that acts on a surface in a direction perpendicular to it, is known as thrust.
  • Pressure: The force acting on per unit area, applied to an object in the direction perpendicular to the surface is called pressure.
  • Liquids exert pressure on the walls of the container in which they are kept.
  • Gases exert pressure in all directions.

  • Atmospheric Pressure: The pressure exerted by atmospheric air around us is known as atmospheric pressure.