Physics Form 4

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 mass. 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

resistmenentang/ melawan

How could this HAPPENs ???

If the object is moving…. 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 an object is at rest…

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

 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

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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 inertia Some 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

ANSWER

When the cardboard covering the glass is pulled out quickly, what will happens to the coin?

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.