Pseudo Force - Definition, Explanation, FAQs

The pseudo force, otherwise known as fictitious force, signifies an imaginary force coming into being when relating to non-inertial reference frames such as accelerating or rotating systems. The acceleration of the observer causes such pseudo forces and not any real interaction; appears to act opposite to the motion of the reference frame. It is well experienced when pushed back by a speeding car or thrown outward by a spinning merry-go-round.

JEE Main 2025: Physics Formula | Study Materials | High Scoring Topics | Preparation Guide

JEE Main 2025: Syllabus | Sample Papers | Mock Tests | PYQs | Study Plan 100 Days

NEET 2025: Syllabus | High Scoring Topics | PYQs

What is Pseudo Force?

An apparent force or pseudo force generally works on all masses whose motion can be described by using a rotating reference frame or some other noninertial frame of reference. Thus, pseudo force defined as a frame of reference should simply accelerate relative to some non-accelerating frame. Rather than any kind of physical interaction between two objects, the force F is generated due to the acceleration 'a' of the non-inertial reference frame. As frames, pseudo forces can accelerate in any direction.

Pseudo Force Formula

The mass and acceleration of an object determine the net force acting on it. In a similar vein, the pseudo-force formula is as follows:

$$
F_p=-m a
$$
Where,
$F_p=$ Pseudo force acting on an item.
$\mathrm{m}=$ mass of an object.
$a=$ acceleration of the frame of reference of an item.
A negative sign suggests that a pseudo force is acting in opposition to the frame of reference acceleration of an item.

Also Read:

• NCERT Exemplar Solutions for All Subjects
• NCERT Notes For All Subjects
• NCERT Solutions for All Subjects

Examples

A straight line of Speed

Every time a car accelerates quickly, it is natural to feel "pushed back into the seat." In an inertial frame of reference with respect to the road, there is no pull on the driver in the backward direction. The acceleration of the car creates a frictional force pushing the backwards in the non-inertial reference frame of the driver.

Elevator Scenario

Let us consider a scenario where a person having mass m is standing on a weighing machine that is placed in a stationary elevator. The actual weight of a person is mg. The weighing machine offers a normal reaction N, the weight ' mg ' is a reading of this machine. The motion of the elevator decides the weight of the man.

Difference Between Pseudo Force and Real Force