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Inertia, Meaning (SPM Physics)

The tendency of an object to resist any change to its state of rest or uniform motion.

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EnglishInertia
Bahasa MelayuInersia
中文惯性

Definition

The tendency of an object to resist any change to its state of rest or uniform motion.

Force and Motion I

In exam terms

Inertia is the tendency of an object to resist any change to its state of rest or of uniform motion. It is a property of matter, not a force, so it has no symbol and no unit.

The larger the mass of an object, the greater its inertia.

Inertia is the idea behind Newton's first law of motion. For example, when a bus brakes suddenly, standing passengers lurch forward because their bodies tend to keep moving at the same velocity, resisting the change in motion.

Do not confuse it with mass

Do not confuse inertia with mass. Mass is the measure of inertia and is a quantity in kilograms (kg); inertia itself is the tendency or property, and it has no unit.

A loaded lorry has more mass and therefore more inertia, so it is harder to start moving or to stop.

In Paper 2 this is usually phrased as explain, in terms of inertia, why…, so your answer must mention the object's tendency to resist a change in its state of motion, not just quote a formula.

Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)

Frequently asked questions

Is inertia a force?
No. Inertia is a property of matter, the tendency to resist a change in motion. It is not a force and has no unit.
How is inertia related to mass?
Mass is the measure of inertia. The greater the mass of an object, the greater its inertia, so it is harder to start or stop.
Why do passengers lurch forward when a bus stops suddenly?
Because of inertia: their bodies tend to keep moving forward at the same velocity and resist the sudden change in motion.

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