Monday, February 18, 2013

First Laws Of Motion and Inertia

Newton’s Law of Motion:
It is also called Law of Inertia. According to this law a body continues to be in the state of rest or
of uniform motion along a straight line unless it is acted upon by some external force.
Inertia:
Inertia is the property of a body by virtue of which it cannot change its state of rest or of
uniform motion along a straight line by itself.
Mass is the measure of inertia. The greater the mass, larger is the inertia and vice-versa.
Types of inertia:
Inertia is of three types:
1. Inertia of rest.
2. Inertia of motion.
3. Inertia of direction.
1. Inertia of rest: The property of a body by virtue of which it cannot change its state of rest,
is known as inertia of rest.
Examples:
i) When branch of a apple tree is shaken, apples fall down. This is because the
branch comes in motion but the apple tends to remain at rest due to inertia of rest.
ii) When a bus suddenly starts moving, the passenger tends to fall backward. This is
because the lower part of the body of the passenger comes in motion with bus but
the upper part tends to remain at rest due to inertia of rest.
2. Inertia of Motion: The property of a body by virtue of which it cannot change its state of
uniform motion along a straight line is known as inertia of motion.
Examples:
1) When a bus stops suddenly, the passenger tends to fall forward. This is because the
lower part of the body of the passenger comes at rest with bus but the upper part of the
body tends to remain in motion due to inertia of motion.
2) A person jumping out of a moving bus may fall forward. This is because the feet of the
person come at rest with ground but the upper part of body tends to remain in motion
due to inertia of motion.
3) An athlete running in a race will continue to run even after reaching the finishing point.
3. Inertia of direction: It is the inability of the body to change its direction of motion by itself.
Examples
When a bus moving along a straight line takes a turn to the right, the passengers are thrown
towards left. This is due to inertia which makes the passengers travel along the same straight
line, even though the bus has turned towards the right.

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