Physics Form 4: Chapter 2 - Newton First Law of Motion (Inertia)

• Inertia is the tendency of an object to remain in its state of rest or of uniform motion in a straight line.
• Law of inertia is also known as Newton's First Law of Motion
• Newton's First Law of Motion state that an object will in its state of rest or of uniform motion in a straight line unless it is acted upon by a net external force.

Examples of effect of inertia:

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. 

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.

For further examples, click on the diagram below to play!