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Chapter 2

Forces And Motion

10

Inertia What is Inertia? • Inertia is the reluctance of an object to stop once it is in uniform motion. • Inertia is also the reluctance of an object to be moved once it is at rest. • Mass is a measurement of the amount of inertia. • The characteristics of inertia can be summarized by Newtonʼs first law of motion. • Newtonʼs first law of motion states that every object will continue in its state of uniform velocity or at rest unless it is acted upon by an external force.

Examples Of Situations Involving Inertia

Hammer

hit

1 2 3

Wooden block Falls down 4

Cardboard Coin Table

5

The reluctance of wooden blocks to be moved

Pull

Glass

The reluctance of a coin to be moved String

Moves with uniform velocity

Stops suddenly

Easy to push

The reluctance of a skater to stop G-clamp Table

Metal rod

Empty bucket

A

B

Bucket filled with sand

Harder to push

An object of greater mass has greater inertia

Inertia balance

Period of oscilllation is longer if more metal rods are used

It is harder for a moving train to stop than a moving motorcycle because the train has greater inertia Force of friction

The safety belt can reduce the negative effect of inertia in an accident

As a book slides across a table from left to right, the force of friction acts on the book to slow it down and bring it to rest © Marshall Cavendish ( Malaysia ) Sdn. Bhd.