SUB-TOPIC:- NEWTON'S FIRST LAW CLASS:- IX SUBJECT :- SCIENCE. (PHYSICS)

1. Students will learn & differentiate between the term "bodies at rest "& "bodies in motion.“ 2. They will understand & explain the scientific meaning of "FORCE.“ 3. They will understand the cause of common day to day events that are caused by the application of NEWTON'S first law. 4. They will be able to explains he property of "INERTIA".

Before understanding this law we should be quite clear in our mind about the concept of Bodies in the state of "rest“ and bodies in the state of“ motion." Regarding the bodies in the state of motion we should have no doubt as we see various objects moving in our surroundings such as movement of cars, bus, cycle, children playing football, cricket etc.. But if we closely examine the bodies in the state of rest we will find no object at rest because earth is constantly revolving, motions of atoms & molecules & even electrons revolving around the nucleus of atoms in definite orbits. So to understand the concept of rest or motion we have to select some stationary object of reference such as a pole,a tree or a building.

Now it will be very easy to understand the concept of state of bodies whether they are at rest or in motion. If a body does not change its position with respect to the object of reference it is said to be at rest & if it changes its position with respect to the reference object it is in motion. Now it will become very simple to understand the Newton 's first law..It states that every body tends to remain in its state of rest or of uniform motion unless some external force is applied to change that state This tendency of a body to remain in its state of rest or of motion is known as inertia. Therefore this law is also known as the LAW OF INERTIA. This law is very important to understand FORCE. Force is that which changes the state of body i.e. from rest to motion & vice versa. Suppose a book is lying on a table or a ball is at rest, to change its state we will have to apply force. Similarly we observe that a moving ball on the ground comes to rest after some time,it means some force is definitely acting on the ball & this is obviously the Frictional force between the surface of ground & the surface of ball.

We find various events in our day to day life. While getting down a moving bus a passenger usually falls forward because his feet on touching the ground immediately comes to rest while the upper part of body is in motion & he falls forward. Therefore while getting down from the moving bus we should run in the direction of the moving bus.

If passengers are sitting in the bus & suddenly the bus starts they will fall backward i.e. their back will strike the seat. This is because of the fact that the lower part Of their body moves in the direction of the bus &the upper part of their body falls backward due to inertia. If we want to remove dirt & soil particles from a bed sheet strong jerk should be given to the bed sheet & due to Inertia dust will be separated. So there are numerous instances where Newton's first law is applied in our day to day activities.