- An inertial force is a force produced by the reaction
of a body to an accelerating force, equal in magnitude and opposite
in direction to the accelerating force. An inertial force lasts only
as long as the accelerating force does.
- It is also a force that must be added to the equations of motion when Newton's
laws are used in a rotating or otherwise accelerating frame
of reference. It is sometimes described as a fictional force because
when the same motion is solved in the frame of the external world, the
inertial force does not appear.