Types of inertia
Quantitatively,
inertia of a body is measured by the magnitude of force required to change the
mate of the body. Larger the force required to change the state of the body,
greater is its inertia, It is well known that when a body is heavy, force
required to change its state is large and, therefore, the incrtia of the body
is also large. The reverse is also true. Hence, we conclude that mass of a body
is a measure of Inertia of the body. Larger the mass, greater is inertia. For
example :
1. It is
easier to push an empty box than to push a box full of books. The box full of
books has larger mass and hence greater inertia as compared to the empty box.
2. When
we kick a football , it flies away. Instead, when a stone of same size is
kicked with an equal force, the stone hardly moves. The stone being heavier
than football has larger inertia.
THREE TYPES OF INERTIA
Inertia
of a body is of three types :
(i)
Inertia of rest
(ii)
Inertia of motion
(iii) Inertia
of direction
(i) Inertia of rest
It is the inability of a body to change by itself, its state
of rest. This means a body at rest remains at rest and cannot start moving on
its own. Rather, a body at rest opposes the forces which try to move it.
Examples of inertia of rest
1. When a
bus or train starts suddenly, the person sitting inside tends to fall
backwards. This is because lower part of his body starts moving with the bus or
train, but the upper part of the body tries to remain at rest, due to inertia
of rest.
2. When
we shake vigorously a branch of a mango tree, the mangoes fall down. This is
because on shaking, the branch comes in motion and the mangoes tend to remain
at rest, due to inertia of rest. Therefore, the mangoes get detached and fall.
(ii) Inertia of motion
It is the inability of a body to change by itself, its state
of motion. This means a body in motion remains in motion and cannot stop on its
own. Rather, a body in motion opposes the forces which try to stop it.
Examples of inertia of motion
1. When a
bus or train stops suddenly, a person sitting inside tends to fall forward.
This is because lower part of his body comes to rest with the bus or train, but
the upper part of his body tends to continue its motion, due to inertia of
motion.
2. A
person jumping out of a speeding train may fall forward. This is because on
jumping, his feet come to rest as they touch the ground. But his remaining body
continues to move forward due to inertia of motion.
(iii) Inertia of direction
It is the inability of a body to change by itself its
direction of motion, i.e., a body moving along a straight line will continue to
move along the same direction unless some external force co pels it to change
the direction of motion. Rather, a body opposes the forces that try to change
its direction of motion.
Examples of inertia of direction
1. When a
car rounds a curve suddenly, a person sitting inside is thrown outwards. This
is because while the car turns, the person tries to maintain his original
direction of motion due to inertia of direction.
2. When a
vehicle passes through mud, the rotating wheels of the vehicle throw out mud
tangentially due to directional inertia. The mud guards over the wheels stop
this mud protecting the clothes of the driver of the bike/motor bike.
Points which should be learn
1. From
his observations, Galileo established that an unbalanced external force is
required to initiate the motion (from state of rest). But no unbalanced force
is needed to sustain the uniform motion. Objects continue moving with a
constant speed along a straight line, when no external force acts on them.
2.
According to Newton's first law of motion, a body continues to be in a state of
rest or in a state of uniform motion along a straight line, unless an external
force is applied on the body to change the state.
3.
Newton's first law of motion gives us qualitative definition of force. Further,
this law means that a body on its own, cannot change its state of rest or state
of uniform motion along a straight line. This property is called inertia.
Therefore, Newton's first law of motion is also called the law of inertia.
4.
Quantitatively, inertia of a body is measured by the magnitude of force
required to change the state of the body. When body is heavy, force required to
change its state is large. Therefore, a heavy body has large inertia. Hence
mass of a body is a measure of inertia of the body in linear motion. Larger the
mass, greater is the inertia.
5.
Inertia of a body is of three types : (i) Inertia of rest (ii) Inertia of
motion and (iii) Inertia of direction.
Inertia
of rest means that a body at rest cannot start moving on its own. Inertia of
motion means that a body in motion cannot stop on its own.
Inertia
of direction means that a body moving along a particular direction cannot
change its а direction of motion by itself.
In all
the three cases, external forces are required for changing the state of the
body.
6. From
his observations, Galileo established that an unbalanced external force is
required to initiate the motion (from state of rest). But no unbalanced force
is needed to sustain the uniform motion. Objects continue moving with a
constant speed along a straight line, when no external force acts on them.
7.
According to Newton's first law of motion, a body continues to be in a state of
rest or in a state of uniform motion along a straight line, unless an external
force is applied on the body to change the state.
8.
Newton's first law of motion gives us qualitative definition of force. Further,
this law means that a body on its own, cannot change its state of rest or state
of uniform motion along a straight line. This property is called inertia.
Therefore, Newton's first law of motion is also called the law of inertia.
9.
Quantitatively, inertia of a body is measured by the magnitude of force
required to change the state of the body. When body is heavy, force required to
change its state is large. Therefore, a heavy body has large inertia. Hence
mass of a body is a measure of inertia of the body in linear motion. Larger the
mass, greater is the inertia.
10.
Inertia of a body is of three types : (i) Inertia of rest (ii) Inertia of
motion and (iii) Inertia of direction.
Inertia
of rest means that a body at rest cannot start moving on its own. Inertia of
motion means that a body in motion cannot stop on its own.
Inertia
of direction means that a body moving along a particular direction cannot
change its а direction of motion by itself.
In all
the three cases, external forces are required for changing the state of the
body.
0 Comments