Understanding Inertia

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Malaysia SPM Form 4, Chapter 2: Force and Motion
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UNDER CONSTRUCTION

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1 Mass
2 Inertia
3 Newton's First Law
4 Inertia in Daily Life
5 Mass and Inertia
- 5.1 Bucket of Greater Mass is More difficult to be Moved
- 5.2 Empty cart is easier to be moved
6 Frequenly Asked Question
7 Additional notes
8 External Links

[edit] Mass

Mass is defined as the amount of matter. The SI unit of mass is kilogram (kg) Mass is a scalar quantity.

[edit] Inertia

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

[edit] 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).

[edit] Inertia in Daily Life

[edit] 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.

[edit] 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.

[edit] Pulling a Thread

1. 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

2. 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.

[edit] Mass and Inertia

[edit] Bucket of Greater Mass is More difficult to be Moved

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.

[edit] 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.