Download - 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.