FORM 4: 2.3 UNDERSTANDING INERTIA

THE MEANING OF INERTIA

The inertia of an object is the tendency of the object to remain at rest or, if moving, to continue its uniform motion in a straight line.

NEWTON’S FIRST LAW

The concept of inertia was explained by Sir Isaac Newton in the first law of motion.

Newton’s first law states that every object continues in its state of rest or of uniform motion unless it is acted upon by an external force.

RELATIONSHIP BETWEEN MASS AND INERTIA

The larger the mass, the larger its inertia.

SITUATIONS INVOLVING INERTIA

APPLICATIONS OF THE CONCEPT OF INERTIA

APPLICATIONS	EXPLANATION
If the bottom of the handle of a hammer is knocked downwards against a hard surface, the loose head of the hammer tightens in its wooden handle.	The hammer head continues with its downward motion after the handle has come to a stop. This causes the upper part of the wooden handle to slot deeper into the hammer head.
When the branch of an apple is shaken, the apples fall to the ground.	The apples which are stationary tend to remain at rest when the branch is shaken. As a result, the stalks are strained and the apples break away from the branch.
Animals such as dogs and cats shake their body vigorously to dry their wet fur.	The droplets of water on the fur tend to continue in motion when the furs are reversed in direction during shaking. As a result, water droplets are separated from the fur and fall off.

WAYS OF REDUCING THE NEGATIVE EFFECTS OF INERTIA

EFFECTS OF INERTIA	WAYS OF REDUCING
If a car crashes while travelling, the passengers will crash into the parts of the car immediately in front of them and suffer injuries.	Seat belts help to tighten the passenger during collision. This is to prevent the passenger from being thrown forward due to inertia.
	Air bag is fitted inside the steering wheel. It provides a cushion to prevent the driver from hitting the steering wheel.
The objects will fall off the lorry when the lorry starts moving.	The objects must be securely fastened to the lorry so that the objects become part of the carrier.
If a loaded lorry stops abruptly, its heavy load, for example, timber logs will continue to move forward towards the driver’s cabin because of its massive inertia.	A strong iron structure between the driver’s cabin and the load ensures the driver’s safety.