Pseudo force is an unreal or fictitious force.Pseudo force is experienced when the observer is present in an accelerated system.Pseudo Force is a mathematical adjustment in the Newton's Equations of Motion.When we calculate net force acting on an object in relative frame, we add or subtract pseudo force. In the ground frame, it is observed by the person but in relative frame, one does not see the force being applied but the effect can be seen.

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a pseudo force,d'Alembert force, or inertial force is a force that appears to act on a mass whose motion is described using a non-inertial frame of reference, such as an accelerating or rotating reference frame. An example is seen in a passenger vehicle that is accelerating in the forward direction - passengers perceive that they are acted upon by a force in the rearward direction pushing them back into their seats. An example in a rotating reference frame is the force that appears to push objects outwards towards the rim of a centrifuge. These apparent forces are examples of fictitious forces.