Pseudo Force - Definition, Explanation, FAQs

Edited By Vishal kumar | Updated on Jul 02, 2025 05:00 PM IST

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.

Pseudo Force - Definition, Explanation, FAQs

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.

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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.

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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

Pseudo Force	Real Force
A pseudo force is one that develops as a result of the observer's frame of reference speeding up.	Real force is defined as a force that is created as a result of an interaction between objects.
Newton's law of motion is not followed by pseudo force.	Newton's law of motion is observed by real force.
Force felt when a car suddenly accelerates (backward push), centrifugal force in a rotating frame	Gravitational force, tension in a rope, friction, normal force.

Frequently Asked Questions (FAQs)

1. What is fictitious force?

Fictitious force is a false force introduced to solve the questions.

2. What is another name for pseudo force?

Another name for pseudo force is fictitious force or false force.

3. What is pseudo force meaning in Hindi?

मिथ्या

4. What is the pseudo force definition?

Pseudo force is a force which converts non inertial frame of reference to inertial frame of reference.

5. What is a pseudo force formula?

F(p) = mass x acceleration

6. Can pseudo forces be eliminated?

Pseudo forces can be eliminated by switching to an inertial reference frame. In an inertial frame, all motion can be explained using only real forces, and pseudo forces disappear. However, in some cases, using a non-inertial frame with pseudo forces can simplify the analysis of a problem.

7. How do pseudo forces relate to Einstein's equivalence principle?

Einstein's equivalence principle states that the effects of gravity are indistinguishable from the effects of acceleration. This means that the gravitational force in an inertial frame is equivalent to a pseudo force in an accelerating frame. This principle was crucial in the development of Einstein's general theory of relativity.

8. What is the relationship between pseudo forces and inertia?

Pseudo forces are directly related to inertia. They arise because objects in a non-inertial frame tend to maintain their state of motion relative to an inertial frame (due to inertia), which appears as an additional force in the non-inertial frame. The magnitude of pseudo forces is proportional to the mass of the object, just like inertial forces.

9. Can pseudo forces ever cancel out real forces?

In a non-inertial frame, pseudo forces can appear to cancel out real forces. For example, in free fall, the pseudo force due to acceleration exactly cancels the gravitational force, making objects appear weightless. However, this cancellation is only apparent in the accelerating frame and doesn't represent a true physical cancellation of forces.

10. How do pseudo forces affect the behavior of a pendulum on a rotating platform?

On a rotating platform, a pendulum experiences pseudo forces that alter its behavior. The Coriolis force causes the plane of oscillation to rotate relative to the platform (an effect known as Foucault precession), while the centrifugal force modifies the pendulum's equilibrium position and period of oscillation.

11. What is the difference between centrifugal and centripetal force?

Centripetal force is a real force that acts towards the center of a circular path, keeping an object in circular motion. Centrifugal force is a pseudo force that appears to act outward in a rotating frame of reference. While centripetal force actually exists, centrifugal force is only apparent in the rotating frame and doesn't exist in an inertial frame.

12. Can pseudo forces do work?

Yes, pseudo forces can do work in a non-inertial reference frame. Although they're not "real" forces, their effects are observable in the non-inertial frame, and they can cause objects to move and thus perform work within that frame. However, this work doesn't correspond to a change in the total energy of the system when viewed from an inertial frame.

13. How do pseudo forces relate to Newton's laws of motion?

Pseudo forces are introduced to allow Newton's laws of motion to be applied in non-inertial reference frames. In these frames, objects appear to accelerate without any apparent force, which would violate Newton's first law. By introducing pseudo forces, we can account for this apparent acceleration and maintain the validity of Newton's laws in the non-inertial frame.

14. How do pseudo forces affect the apparent weight of an object?

Pseudo forces can change the apparent weight of an object in a non-inertial frame. For example, in an elevator accelerating upward, you feel heavier because the pseudo force acts downward, adding to your actual weight. Conversely, in a downward accelerating elevator, you feel lighter because the pseudo force acts upward, opposing your weight.

15. What is the role of pseudo forces in the design of amusement park rides?

Pseudo forces play a crucial role in the design of amusement park rides. Rides like roller coasters and centrifuges create accelerating reference frames where passengers experience pseudo forces. These forces contribute to the thrilling sensations of the rides. Engineers must carefully calculate these forces to ensure the rides are both exciting and safe.

16. What is a pseudo force?

A pseudo force, also known as a fictitious force, is an apparent force that appears to act on objects in non-inertial reference frames. It's not a real force, but rather the result of observing motion from an accelerating frame of reference. Pseudo forces are introduced to explain the apparent motion of objects in these non-inertial frames.

17. Why are pseudo forces called "fictitious"?

Pseudo forces are called "fictitious" because they don't arise from any physical interaction between objects. They only appear in non-inertial reference frames and are used to explain motion in these frames using Newton's laws. In an inertial frame, these forces don't exist, which is why they're considered not "real" in the same way as forces like gravity or electromagnetism.

18. How does a pseudo force differ from a real force?

A real force is caused by the interaction between two objects and exists in all reference frames. A pseudo force, on the other hand, only appears in non-inertial reference frames and isn't caused by any physical interaction. Real forces obey Newton's third law of motion, while pseudo forces do not have an equal and opposite reaction.

19. Can you give an example of a common pseudo force?

A common example of a pseudo force is the centrifugal force. When you're in a car that's turning, you feel pushed towards the outside of the turn. This apparent outward force is the centrifugal force, a pseudo force that appears in the rotating frame of reference of the car.

20. Are pseudo forces observable?

Yes, pseudo forces are observable in non-inertial reference frames. While they don't exist in inertial frames, they can be felt and their effects can be measured in accelerating frames. For instance, passengers in a bus feel pushed backwards when the bus accelerates forward, which is the effect of a pseudo force.

21. How do pseudo forces affect the pressure distribution in a rotating fluid?

In a rotating fluid, pseudo forces (mainly the centrifugal force) affect the pressure distribution. They cause the pressure to increase from the axis of rotation outward, creating a pressure gradient. This effect is used in centrifuges to separate fluids of different densities and in the formation of tropical cyclones in the atmosphere.

22. How do pseudo forces affect the precession of a spinning top?

In the rotating frame of a precessing top, pseudo forces contribute to the complex motion. The Coriolis force, in particular, plays a role in maintaining the precession

23. What is the mathematical expression for a pseudo force?

The general expression for a pseudo force (F_p) acting on an object of mass m in a non-inertial frame is:

24. How does Earth's rotation create a pseudo force?

Earth's rotation creates a pseudo force called the Coriolis force. This force appears to deflect moving objects to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. It affects large-scale motions like ocean currents and wind patterns but is typically negligible for small-scale, everyday motions.

25. How do pseudo forces affect fluid motion on a rotating planet?

On a rotating planet like Earth, pseudo forces (particularly the Coriolis force) significantly affect large-scale fluid motions such as ocean currents and atmospheric circulation. These forces cause deflections in the motion of air and water, leading to phenomena like the rotation of hurricanes and the formation of gyres in oceans.

26. What is the pseudo force experienced in a rotating space station?

In a rotating space station, occupants would experience a centrifugal pseudo force directed outward from the axis of rotation. This force mimics gravity, allowing astronauts to "stand" on the inner surface of the station. The magnitude of this force depends on the station's angular velocity and the distance from the rotation axis.

27. How do pseudo forces affect the motion of projectiles on Earth?

The Coriolis force, a pseudo force due to Earth's rotation, affects the motion of long-range projectiles. It causes a slight deflection to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This effect is significant for long-range artillery and intercontinental ballistic missiles but negligible for everyday throwing or shooting.

28. How do pseudo forces affect the shape of planetary bodies?

Pseudo forces, particularly the centrifugal force due to rotation, affect the shape of planetary bodies. They cause planets to bulge at the equator and flatten at the poles. This effect is more pronounced in faster-rotating planets. On Earth, this results in the planet being an oblate spheroid rather than a perfect sphere.

29. Can pseudo forces ever point towards the center in circular motion?

In circular motion, the commonly experienced pseudo force (centrifugal force) points outward. However, if the frame is rotating faster than the object's circular motion, a pseudo force can appear to point inward. This situation is less common but can occur in certain rotating reference frames.

30. What is the pseudo force experienced in an elevator starting to move upward?

When an elevator starts moving upward, occupants experience a downward pseudo force in addition to their weight. This force is equal to the mass of the person multiplied by the elevator's acceleration. It makes the occupants feel momentarily heavier until the elevator reaches a constant velocity.

31. How do pseudo forces affect the motion of objects on a merry-go-round?

On a merry-go-round, objects experience two main pseudo forces: the centrifugal force pushing outward, and the Coriolis force affecting objects moving radially. These forces combine to create the characteristic curved paths of objects sliding on the merry-go-round's surface and contribute to the sensation of being pushed outward.

32. Can pseudo forces ever be greater than real forces?

Yes, pseudo forces can be greater than real forces in a sufficiently accelerated frame. For example, in a centrifuge rotating at high speed, the centrifugal force can far exceed the gravitational force. This principle is used in centrifuges to create "artificial gravity" many times stronger than Earth's gravity.

33. How do pseudo forces affect the apparent path of light in a rotating frame?

In a rotating frame, pseudo forces don't directly affect light (as light has no mass), but they do affect our perception of light's path. Light travels in straight lines in inertial frames, but in a rotating frame, these straight paths appear curved. This effect is similar to how the path of a ball appears curved when thrown on a rotating platform.

34. What is the pseudo force experienced by a person in a car accelerating in a straight line?

When a car accelerates in a straight line, a person inside experiences a pseudo force in the opposite direction of the acceleration. If the car accelerates forward, the person feels pushed backward. This force is proportional to the person's mass and the car's acceleration.

35. How do pseudo forces affect the formation of weather systems?

Pseudo forces, particularly the Coriolis force, play a crucial role in the formation of large-scale weather systems. They cause wind patterns to curve, leading to the circular motion in cyclones and anticyclones. The Coriolis force is also responsible for the direction of rotation of hurricanes (counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere).

36. Can pseudo forces ever act perpendicular to the direction of acceleration?

Yes, the Coriolis force, a type of pseudo force, acts perpendicular to both the velocity of an object and the axis of rotation of the reference frame. This perpendicular action is what causes the deflection of moving objects in rotating frames, such as the apparent deflection of winds and ocean currents on the rotating Earth.

37. How do pseudo forces affect the behavior of a gyroscope?

In a rotating frame, pseudo forces affect a gyroscope's behavior by inducing precession and nutation. The Coriolis force, in particular, causes the gyroscope's axis to precess. However, the gyroscope's high angular momentum makes it resist these effects, which is why gyroscopes are used for stabilization and navigation in rotating systems.

38. What is the pseudo force experienced by a person in an accelerating rocket?

A person in an accelerating rocket experiences a pseudo force opposite to the direction of acceleration. If the rocket is accelerating upward, the person feels a downward pseudo force in addition to their weight. This can create the sensation of increased gravity, with the total apparent weight being the sum of the actual weight and the pseudo force.

39. How do pseudo forces affect the motion of satellites orbiting a rotating planet?

For satellites orbiting a rotating planet, pseudo forces (mainly the Coriolis force) affect their apparent motion when viewed from the planet's surface. These forces cause the satellite's ground track to shift westward with each orbit. However, in the inertial frame of space, the satellite's orbit is not affected by these pseudo forces.

40. Can pseudo forces ever be attractive?

While pseudo forces are typically repulsive (like the outward-pointing centrifugal force), they can appear attractive in certain situations. For example, in a frame rotating faster than an object's circular motion, or in a frame decelerating linearly, the pseudo force can appear to point inward or forward, respectively, seeming attractive relative to the frame's motion.

41. How do pseudo forces affect the behavior of a Foucault pendulum?

The Foucault pendulum demonstrates the effect of the Coriolis force due to Earth's rotation. This pseudo force causes the plane of the pendulum's swing to rotate slowly. The rate of this rotation depends on the latitude, with a complete rotation taking 24 hours at the poles and longer times at lower latitudes.

42. What is the pseudo force experienced in a car going around a banked curve?

In a car going around a banked curve, passengers experience a combination of pseudo forces. The main one is the centrifugal force pushing outward from the center of the curve. There's also a component of the centrifugal force pushing down the bank due to the inclination. These forces combine with gravity to determine the apparent forces on the passengers.

43. How do pseudo forces affect the formation of planetary rings?

Pseudo forces, particularly the centrifugal force, play a crucial role in the formation and maintenance of planetary rings. In the rotating frame of the planet, the outward centrifugal force balances the inward gravitational force, allowing ring particles to maintain stable orbits. This balance determines the structure and dynamics of the ring system.

44. Can pseudo forces ever vary with position in a reference frame?

Yes, pseudo forces can vary with position in a non-inertial reference frame. For example, in a rotating frame, the magnitude of the centrifugal force increases with distance from the axis of rotation. Similarly, the Coriolis force depends on the velocity of an object relative to the rotating frame, which can vary with position.

45. How do pseudo forces affect the apparent gravity on different parts of Earth?

Pseudo forces, mainly the centrifugal force due to Earth's rotation, affect the apparent gravity at different locations on Earth. This force is strongest at the equator and zero at the poles, causing a slight reduction in apparent gravity at the equator. This effect, combined with Earth's equatorial bulge, results in about a 0.3% difference in surface gravity between the equator and poles.

46. What is the pseudo force experienced by a person in a rotating space habitat?

In a rotating space habitat, a person experiences a centrifugal pseudo force that mimics gravity. This force acts radially outward from the axis of rotation and its magnitude increases with distance from the axis. The rotation rate and radius are typically designed to produce a force equivalent to Earth's gravity on the habitat's outer rim.

47. How do pseudo forces affect the motion of objects dropped in a rotating frame?

Objects dropped in a rotating frame experience pseudo forces that alter their apparent path. The Coriolis force causes the object to deflect sideways as it falls, while the centrifugal force causes it to fall "outward" relative to the rotation axis. The resulting path, as seen in the rotating frame, is a curve rather than a straight line.

48. Can pseudo forces ever cancel each other out?

Yes, pseudo forces can cancel each other out in certain situations. For example, in a rotating frame that's also accelerating linearly, the centrifugal force and the pseudo force due to linear acceleration could potentially cancel each other at certain points. However, this cancellation would generally only occur at specific locations or instants.

49. How do pseudo forces affect the shape of water's surface in a rotating container?

In a rotating container, pseudo forces (mainly the centrifugal force) cause the surface of water to form a parabolic shape. The water climbs up the sides of the container, with the surface curving upward from the center. This shape results from the balance between the outward centrifugal force and the downward gravitational force.

50. What is the pseudo force experienced by a person in an elevator that suddenly stops?

When an elevator suddenly stops, a person inside experiences an upward pseudo force. This force is equal to the person's mass multiplied by the elevator's deceleration. It creates a momentary sensation of being pushed upward or feeling lighter, which is opposite to the feeling when the elevator starts moving upward.