CHAPTER 2.3 UNDERSTANDING INERTIA

LEARNING OUTCOME By the end of the lesson, each student should be able to: Explain what inertia is Relate mass to inertia Give examples of situations involving inertia Suggest way to reduce negative effect of inertia

LEARNING OUTCOME 1: EXPLAIN WHAT INERTIA IS. Inertia is a property of a body that tend to maintain its original state of motion

Inertia can be explain by Newton’s first law of motion “In the absence of external force, an object at rest will remain at rest and object in motion will remain its motion with constant velocity in a straight line”

-Moving with constant velocity State of motion - Stationary (object at rest) -Moving with constant velocity

From Newton’s First Law, an object at rest will remain at rest if there are no external force acting on it

will not stop unless I apply a force by pressing the brake object in motion will remain its motion with constant velocity in a straight line unless there was external force acting on it. My superbike will not stop unless I apply a force by pressing the brake

LEARNING OUTCOME 2: RELATE MASS TO INERTIA The pail fill with sand is more difficult to push compare to empty pail. When they start swinging, the pail fill with sand is more difficult to stop compare to empty pail A B

Which person has more mass, the fat man or the little boy? Which one has greater inertia? Relate mass and inertia

When the cardboard is pulled away quickly, the coin drops straight into the glass. The inertia of the coin maintains its state at rest. The coin falls into the glass due to gravity. Learning Outcome 3: Give example of situation involving inertia

Chili sauce in the bottle can be easily poured out if the bottle is moved down fast with a sudden stop. The sauce inside the bottle moves together with the bottle. When the bottle stops suddenly, the sauce continue in its state of motion due to the effect of its inertia.

Body moves forward when the car stops suddenly The driver were in a state of motion when the car was moving. When the car stopped suddenly, the inertia in the passengers made them maintain their state of motion. Thus when the car stop, the passengers moved forward.

LEARNING OUTCOME 4: SUGGEST WAY TO REDUCE NEGATIVE EFFECT OF INERTIA

Why we need to wear seat belt?

Furniture carried by a lorry normally are tied up together by string Furniture carried by a lorry normally are tied up together by string. When the lorry starts to move suddenly, the furniture are more difficult to fall off due to their inertia because their combined mass has increased.

Lets try some questions

Inertia of an object is A the friction force exerts to the object B the friction force exerts to the object C the force against the motion of the object D the property of the object which resists a change in its motion.

2 What is the name of the property of a body which resists a change in its state of rest or of uniform motion? A Inertia B Density C Velocity D Acceleration

Which object has the greatest inertia?

4 How difficult is it to start a heavy lorry moving and to stop it moving ? to move to stop A difficult difficult B difficult easy C easy difficult D easy easy

Homework Please answer question in your Physics text book Page : 32 Discuss your answer with mentor/mantee.