Ch – 11 Force & Pressure

Important Points:

• A push or pull on an object is known as force.
• At least two objects must interact for a force to come into play.
• Forces applied on an object in the same direction add to one another.
• If two forces act in the opposite directions on an object, the net force acting on it is the difference between the two forces.
• The strength of the force is expressed by its magnitude.
• Force effects the speed of an object.
• If the force applied on the object is in the direction of its motion, the speed of the object increases.
• If the force is applied in the direction opposite to the direction of motion, then it results in a decrease in the speed of the object.
• A change in either the speed of an object, or its direction of motion, or both, is described as a change in its state of motion.
• The state of motion of an object is described by its speed and the direction of motion.
• The state of rest is considered to be the state of zero speed.
• Force on an object may change its shape.
• Muscular force enables us to perform all activities involving movement or bending of our body.
• If a force acts on an object with being in contact with it is known as contact force.
• If a force acts on an object without being in contact with it is known as non-contact force.
• The force of friction or frictional force always acts on all the moving objects and its direction is always opposite to the direction of motion.
• The force exerted by a magnet is known as magnetic force.
• Objects or things fall towards the earth because of the force of gravity or gravitational force.
• The force exerted by a charged body on another charged or uncharged body is known as electrostatic force.
• The force acting on a unit area of a surface is called pressure.
• Pressure = force/area on which it acts
• The pressure exerted by atmosphere is known as atmospheric pressure.