KERALA PSC / PHYSICS / FORCE / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

 

KERALA PSC / PHYSICS / FORCE / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

KERALA PSC / PHYSICS / FORCE / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES

·      Force is any influence that tends to change the state of rest or the uniform motion in a straight line of a body.

·      F = ma

·      Unit of force is Newton

·      Four basic forces in nature: Gravitational, electric, strong force and weak force

·      Strong forces are nuclear forces that keep the nucleons together inside the nucleus. Strong forces are charge independent.

·      Weak forces are nuclear forces between electron and neutrino

·      The force acting for a very short time is called an impulsive force. It is measured as the rate of change in momentum. Eg: force exerted on a bullet when it is fired with a gun

·      Impulse of a force is the product of the force and the time during which the force acts on the body.

·      The force of attraction between like molecules is called cohesion

·      The force of attraction between unlike molecules is called adhesion

·      Friction is the result of molecular interaction. It is due to the force of attraction between the molecules on the two surfaces in contact. This force of attraction is called adhesive force.

·      Weight can be defined as the force with which earth attracts a body. Weight, w = m×g

·      Mass remains constant while weight varies from place to place

·      Friction is a force that resists the movement of one surface over another

·      Kinetic friction between two surfaces in contact is the force of friction which comes into play when there is relative motion between the surfaces

·      Rolling friction between two surfaces in contact is the force of friction which comes into play when a body rolls over another. This is the principle on which ball bearings work.

·      Due to the existence of friction we can walk on the ground, trains can run on rails.

·      Frictional force offered by air helps the parachute to have a slow landing

·      Friction offered by atmosphere air is protecting us from being hit by meteors

·      A lubricant is a substance which forms a thin layer between two surfaces in contact.

·      Generally, oil and grease are used as lubricants to reduce friction as well as to protect the moving parts from overheating. A modern lubricant is a mixture of mineral oil, vegetable oil and colloidal thin oil. Flow of compressed pure dry air acts as lubricant.

·      The force required by a revolving body is called centripetal force

·      When a man circles round the earth in a spacecraft, his mass remains constant but weight becomes zero

·      The upward force which liquid act on bodies immersed in it is called buoyant force.

·      Two object losing the same weight when immersed in water must have the same density.

·      Centrifugal force helps to separate cream from milk.

 

KERALA PSC / PHYSICS / FORCE / OBJECTIVE QUESTIONS / STUDY MATERIALS / GENERAL KNOWLEDGE / KERALA PSC PRELIMINARY / NOTES