PHYSICS FORM 4

INERTIA

OBJECTIVES

• To know the exactly definition of inertia.

• To analyze the relationship between inertia and mass.

• To understand the effects of inertia in daily life experience.

MENU

• Definition of inertia• Relationship between mass inertia and m

ass.• Effect of inertia in our daily life• Quiz • Reference

Magic or trick !!!

INERTIA

Inertia is the property of matter that cause it to resist any change in its motion or state of rest

resistmenentang/ melawan

How could this HAPPENs ???

INERTIA makes the moving object continue to move at a constant speed in the same direction unless some external force changes the object’s motion

If the object is moving….

It tends to stay in that position unless some force puts that object into motion

If an object is at rest…

Inertia is not physical quantity and thus it does not have units

The property of inertia is found from the Newton’s first law of motion

Newton’s First Law of Motion

"An object at rest tends to stay at rest and an object in motion the same speed and in the same direction tends to stay in motion with unless acted upon by an unbalanced force"

RELATIONSHIP BETWEEN INERTIA

AND MASS

•Constant wherever it is measured

•Base quantity•Scalar quantity•The SI unit of mass is

kilogram (kg)

Mass can influence the

effects of inertia.

An object with a larger mass has a

larger inertia.

mass inertia

YOU WANT TO KNOW THE

EXPLANATION ABOUT THIS???

CLICK ON THE VIDEO

If the motorcycle were to abruptly stop, then the rider in motion would continue in motion. The rider would likely be propelled from the motorcycle and be hurled into the

air. Once they leave the motorcycle, the rider becomes a projectile and continues in

projectile-like motion. It is because of inertia.

Applications of inertiaSome examples of using inertia in our daily life are :

1. The looses head of a hammer • To tighten the loose head of a hammer, knock one end of

the handle held vertically, on a hard surface. • The hammer head will continue on its downward motion• when the handle has been stopped, the top end of the

handle is slotted deeper into the hammer head.

2. The wet fur of cats and dogs.• Cats and dogs dry their wet fur by shaking their body

vigorously. • Water droplets on the fur tend to continue in motion when the

body has stopped shaking. • water droplets will be separated from the fur and fall away

3. To dislodge sticking chili sauce • Chili sauce in a bottle is poured out by a quick downward

movement of the bottle followed by a sudden stop. • The sauce in the bottle moves with the bottle during the

downward movement. • When bottle is stopped, the inertia of the sauce causes it to

continue on its downward movement and thus the sauce is forced out of the bottle.

4. Passengers in a bus • Passenger in a bus will lurch backward when a stationary bus

starts to move with forward acceleration. • The passenger were originally stationary. • When the bus started to move forward with an acceleration,

the inertia in the passenger made them maintain their original position.

QUIZ

Question 1

Question 2

Question 3

When the cardboard covering the glass is pulled out quickly, what will

happens to the coin?

ANSWER

When the cardboard covering the glass is pulled out quickly, the coin resting on the cardboard drops into

the glass

What will happen to the rest of the coins when one

of the coin is moved out quickly?

ANSWER

The inertia of the coins maintains it in its original

position (at horizontal/rest) even when one of the coin

is moved out quickly

When a student is riding a bicycle and runs over a

stone, he is thrown forward. Why does this happen?

ANSWER

THE INERTIA OF THE STUDENT MAINTAINS HIS

FORWARD MOTION SO THAT HE IS THROWN FORWARD WHEN HIS

BICYCLE IS MOMENTARILY STOPPED BY THE STONE

References

• FOCUS SUPER HOT SPM PHYSICS- S.L Chang, Koay Kheng Chuan, Yew Kok Leh. Penerbitan Pelangi Sdn. Bhd.