Definition “If the body is at rest, it will remain at rest,if it is in motion it will continue in motion with constant speed in a straight line unless there is a net force acting upon it.”

This Law tell us about : i) The principle of inertia ii) Definition of force

i) The principle of inertia: First part of the law states that if a body be at rest it has the tendency to remain at rest and if a body be moving uniformly in a straight line it has the tendency to remain moving.This is know as inertia of state.

Inertia increases due to increase of mass.

Inertia is of two type (a) Inertia of rest (b) Inertia of motion

Inertia of rest If the body is at rest, it will remain at rest until external force acting upon it. In a train, you fall backward if suddenly the train starts. Because our body is in the inertia of rest,our feet come to motion with the moving train.

Inertia of motion If the body is at motion, it will continue at motion until external force acting upon it We fall forward when the train stops because our feet in contact with the train come to rest along with the train while the upper part of the body due to inertia of motion tends to move forward. This was about first part of law

Definition of force Second part of the law indicates that it is some external agency only which change or tends to change the state of rest or of uniform motion.This external agency is defined as force.

Question 1)While standing in a moving bus, when it suddenly stop we fall a) forward b) backward c) no change d) none of the above 2) When mass decreases, the inertia will a) increase b) decrease c) no change d) zero

3)While we standing in a rest train, and it suddenly starts,we fall a) Forward b) backward c)no change d) none of the above 4)While a ball thrown up from a uniformly moving vehicle, it falls a) On the vehicle b) outside the vehicle c) goes up ward d) none of the above

REFERENCES 1) S.GOEL 2) SCP BOOK OF BOARD OF SECONDARY EDUCATION, ORISSA KABITA SENAPATI UNIT-IX GOVT. BOYS’ HIGH SCHOOL.BBSR.