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OBJECTIVES

🔷To state and explain Newton's 1st law of motion

🔷To find applications for 1st law from daily life

🔷To describe inertia

🔷To tabulate the examples for inertia

🔷To relate mass and inertia of a body

SUMMARY

Sir Isaac Newton(1624-1727), an English scientist and mathematician is famous for his three laws of motion. Among these laws, the 1st law says about inertia, hence this law is also called as law of inertia. Inertia is the tendency of a body to continue in it's state of rest or state of uniform motion. Many examples and applications are there for the 1st law.

Newton’s 1st law of motion

Sir Isaac Newton(1624 – 1727) was an English scientist and mathematician famous for his three laws of motion.

Definition

Every body continues in it’s state of rest or state of uniform motion unless it compelled by an external unbalanced force

What is meant by this?

An object at rest will remain at rest, and an object moving at a constant velocity will continue moving at a constant velocity, unless it is acted upon by an unbalanced force.

For example a soccer ball at rest will remains at rest unless it kick by a player

Unbalanced force

• An unbalanced force can cause an object to start moving, stop moving or changes direction.

• Result in a net force and cause change in the object’s motion.

Ineratia

Inertia is the property of a body by virtue of which it opposes any agency that attempts to put it in motion or, if it is moving, to change the magnitude or direction of its velocity.

There are two types of inertia

1. Inertia of rest

2. Inertia of motion

Inertia of rest

The tendency of a body to continue at rest

Examples -

Examples -

• When the bus stop abruptly, the passengers lurch forward

• A running athlete can not stop himself abruptly at the finishing line in a space

• A wet umbrella is rotated vigorously and then stops abruptly, then water on the umbrella spun off

• A person jumping out of a moving bus falls down if he fails to run

• When pedaling a bicycle, if you stop pedaling, then the cycle continue going for sometimes

• A fan continues it’s motion for sometimes even if we switched off it

• Flying over the handle bars if your cycle stops suddenly

Inertia and mass

• The inertia of an object depends on it’s mass

• When the mass increases inertia also increases

How this can be illustrated?

• It is more difficult to roll a filled drum than an empty one

• It is more difficult to push a car compared to a bicycle

• A bat need to have more velocity to hit a cricket