Laws Of Motion

Inertia
 The property of a body to resist any change is called inertia e. g. when a horse starts suddenly, the rider falls backwards due to the inertia of rest of the upper part of his body.

Newton’s First Law
 Every body continues to be in its state of rest or uniform motion in a straight line, unless compelled by some external force acting on it.
 Example: Any object continues lying where it is, unless it is moved.
 Newton’s first law gives the definition of Inertia.
Momentum:
 Momentum of a body is the product of its mass, m and velocity, v, and is denoted by P.

It is a vector quantity.
 SI unit → kg ms^{−1}
Newton’s Second Law of Motion
 The rate of change of linear momentum of a body is directly proportional to the external force applied on the body, and this change takes place always in the direction of force applied.
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