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Pseudo forces
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In accelerating frames add −ma to apply Newton's laws.
F_pseudo = −maIn an accelerating frame with acceleration a, every body feels an extra force −ma in that frame. Using it, Newton's laws apply as usual in the non-inertial frame.
In a braking car (a = −3 m/s²) a 60 kg passenger feels +180 N forward.
Pseudo forces have no reaction partner.
In more detail
Pseudo forces, such as centrifugal and Coriolis forces, appear in non-inertial frames. They are needed to apply Newton's laws in accelerating or rotating frames.
Real-world uses
- Engineers model motion inside a rotating space station using pseudo forces.
- Weather models include Coriolis effects in rotating-Earth frames.
- A passenger leaning forward in a braking car feels a pseudo force pulling them forward, which is an effect of the car's acceleration.
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Frequently asked questions
Are pseudo forces real?
They are fictitious, but their effects are real to observers in the non-inertial frame.
Why use them?
Because they let you apply Newton's laws directly in a frame that accelerates or rotates.
How do I use a pseudo force in a calculation?
Add the term minus ma to the real forces in the accelerating frame, then apply Newton's second law as usual.
Related topics in Newton's Laws & Forces
Vertical circular motion · Loop-the-loop · Centrifugal force · Drag force · Stokes' law · Terminal velocity of a sphere