# Mass and Inertia

Card 1: What is mass?

## Mass

Mass is the amount of matter.

Unit: kilogram (kg)

Type of quantity: Scalar quantity

Card 2: What is inertia?

## Inertia

Inertia is the property of a body that tends to maintain its state of motion.

Card 3: State Newton's First Law

## Newton's First Law

In the absence of external forces, an object at rest remains at rest and an object in motion continues in motion with a constant velocity (that is, with a constant speed in a straight line).

Card 4: Situation Involving Inertia 1 - Jerking a Card

## Jerking a Card

When the cardboard is jerked quickly, the coin will fall into the glass.

Explanation:

• The inertia of the coin resists the change of its initial state, which is stationary.
• As a result, the coin does not move with the cardboard and falls into the glass because of gravity.
Card 5: Situation Involving Inertia 2 - Pulling a Book

## Pulling a Book

When the book is pulled out, the books on top will fall downwards.

Explanation:

Inertia tries to oppose the change to the stationary situation, that is, when the book is pulled out, the books on top do not follow suit.

Card 6: Situation Involving Inertia 3 - Pulling a Thread

Pull slowly - Thread A will snap.
Explanation:
Tension of thread A is higher than string B.
Tension at A = Weight of the load + Pulling Force

Yank quickly - Thread B will snap.
Explanation:
The inertia of the load prevents the force from being transmitted to thread A, hence causing thread B to snap.

Card 7: Relation ship between mass and inertia

## Larger Mass - Greater Inertia

Bucket filled with sand is more difficult to be moved. It's also more difficult to be stopped from swinging.

Explanation:

Object with more mass offers a greater resistance to change from its state of motion.
Object with larger mass has larger inertia to resist the attempt to change the state of motion.

Card 8: Empty Cart is easier to be moved

## Empty cart is easier to be moved

An empty cart is easier to be moved compare with a cart full with load. This is because a cart with larger mass has larger inertia to resist the attempt to change the state of motion.

Card 9: Empty Card

Card 10: Empty Card

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