CBSE Class 8 Science, Force and Pressure

•  Force: a push or a pull on an object is called force. Force may impart motion to an object.
  it is applied on an object in the same direction add to one another.
•  Magnitude: the strength of a force is usually expressed by its magnitude
  State of motion: The state of motion of an object is described by its speed and the direction of motion.
•  Muscular Force: The force resulting due to the action of muscles is known as the muscular force.
•  Contact Force: The force which is applied when it is in the contact with the object.
•  Non-contact force: The force exerted on an object without touching it known as non contact force.
•  Gravitational force: the attractive force of earth which acts upon all the objects is called force of gravity or gravitational force.
•  Pressure: The force acting on a unit area of a surface is called pressure. It acts perpendicular to the surface on which pressure is exerted.
  Pressure= force/area on which it acts. Lesser the area, greater is the force.
  Both liquids and gases exert pressure on the wall of their containers.
•  Atmospheric pressure: The pressure on the atmospheric air is known as atmospheric pressure. This weight of air column over a unit 1cm2