# Inertia and First Law of Motion

• Inertia is the inability of a body to change its state.
• Inertia of rest is the inability of a body to change its state of rest.
• Inertia of motion is the inability of a body to change its state of motion.
• Inertia of direction is the inability of a body to change its state of direction.
• Inertia of rotation is the inability of a body to change its state of rotation.
• Mass is a measure of inertia of rotation.
• The reference frame is associated with a coordinate system and to measure position & time.
• A frame of reference which is at rest or moving with uniform velocity is inertial frame of reference.
• Newton's laws are applicable directly in inertial frame.
• A frame of reference which is moving with non-zero acceleration is called Non inertial frame of reference.
• Newton's law are not valid in Non inertial frame.
• In non inertial frame a false force called pseudo force has to be applied.
• According to Newton's first law of motion everybody continues to be in its state unless an external force acts on it to change its state.
• Newton's first law of motion gives the concept of inertia.
• No formula is derived in Newton's first law.

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