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Physics Form 4 Chapter 2 Force and Motion I

Original State of Object that is in Motion
2.4 Inertia
Situation 1
1. Inertia is a natural tendency of an object
to oppose any changes to its original state,
whether in the state of rest or state of motion.

Original State of Object
Inertia
that is at Rest
Situation I VIDEO

Figure 2.45
1. When the car is moving, the passengers in the
Chapter
Pull
2 Cardboard car move together.
Glass 2. When the car stops suddenly, the passengers
are thrown forward.
Figure 2.43 3. The inertia of the passengers resists change
of state of motion. As a result, the passengers
1. Figure 2.43 shows a 50 cent coin resting on a continue to move forward.
cardboard that is placed on top of a glass.
2. When the cardboard is pulled quickly, the coin Situation II
hovers over the top of the glass for an instant 1. Figure 2.46 shows how tomato sauce can be
before dropping into the glass. forced out of its bottle. When the bottle is
3. The inertia of the coin resists change of its state moved quickly towards the food, the sauce in
of rest and hence does not move together with the bottle moves together.
the cardboard. Gravitational force pulls it down
into the glass.

Situation II
1. A book placed in the middle of a stack of books
is pulled out horizontally with a quick jerk.

Figure 2.46
2. When the bottle is stopped suddenly, the sauce
will be forced out of the bottle into the food.
Pull 3. The inertia of the sauce resists change of its
state of motion and continues to move out of
Figure 2.44
the bottle.
2. Initially, the books above it tend to stay at rest.
3. The inertia of these books resists change of Relationship Between Mass and Inertia
state of rest and do not move together with 1. The mass of an object is the amount or
the book that is being pulled out. The books quantity of matter in it.
then fall vertically downwards due to the 2. The mass of an object depends on the number
gravitational force. and type of atoms of the object.

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