Inertia Picture

8/12/2019 Inertia Picture

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SITUATION 1

Have you ever stood in a bus which starts suddenly from

rest? You are likely to fall backwards. If the moving bus stops

suddenly, you are likely to fall forward.

SITUATION 2

Have you noticed that a bigger vehicle (Truck) is more

difficult to stop than a light vehicle (Motorcycle)?

What Causes This to Happen?


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Explanation:

When the bus moves suddenly from rest, our

feet are carried forward but the inertia of ourbody tends to keep us at rest. This causes

our body to fall backwards. When the bus

stops suddenly, our feet are brought to rest,but the inertia of our body tends to continue

its forward motion. This causes our body to

fall forward.


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IMPORTANT

The inertia of an object is the tendency of

the object to remain at rest or, if moving, to

continue its uniform motion in a straight line.

The concept of inertia was explained by Sir

Isaac Newton in the first law of motion.


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EXAMPLE OF INERTIA


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Both the car and driver travelling with

very high speed. When the car

stopped suddenly, the inertia of thedriver caused him to be thrown

forward, thus injuring himself.


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When the book is pulled out horizontally with a

quick jerk, the book above tend to stay at

rest due to its inertia.


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The coin hovers over the top of the

glass for an instant before dropping

into the glass. This is because of itsinertia.


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INERTIA AND MASS

It is more difficult to move a lorry than a

bicycle when both are initially at rest. The

lorry has more inertia than a bicycle.

The inertia of a body increases when its

mass increase.


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WAYS TO REDUCE THE NEGATIVE EFFECT OF

INERTIA.

Ways to reduce inertia in vehicle:

1. Seat belts help to tighten the passenger

during collision. This is to prevent thepassenger from being thrown forward due toinertia.

2. Air bag is fitted inside the steering wheel. Itprovides a cushion to prevent the driver fromhitting the steering wheel.


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EXERCISES

1. Fred spends most Sunday afternoons at

rest on the sofa, watching pro football games

and consuming large quantities of food. What

effect (if any) does this practice have uponhis inertia? Explain.


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ANSWER:

Fred's inertia will increase!

Fred will increase his mass if he makes a

habit of this. And if his mass increases, then

his inertia increases.


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2.

Supposing you were in space in a weightless

environment, would it require a force to set

an object in motion?


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ANSWER

Absolutely yes!

Even in space objects have mass. And if they

have mass, they have inertia. That is, an

object in space resists changes in its state of

motion. A force must be applied to set a

stationary object in motion. Newton's laws

rule - everywhere!


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3

Mac and Tosh are arguing in the cafeteria.

Mac says that if he flings the Jell-O with a

greater speed it will have a greater inertia.

Tosh argues that inertia does not dependupon speed, but rather upon mass. Who do

you agree with? Explain why.


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ANSWER

Tosh is correct.Inertia is that quantity which

depends solely upon mass. The more mass,

the more inertia. Momentum is another

quantity in Physics which depends on bothmass and speed. Momentum will be

discussed in a later unit.

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