Can anyone expain to me what fictitious force is?

Answer 1

In the simplest terms, fictitious forces are usually inertia.

Let's put it this way... one of Newton's big revelations was that all reference frames are equally valid from a physics point of view. If you're in space and you see something moving away from you, it's just as valid to say that you're moving and that other thing is stationary. This is a pretty useful idea to physicists.

One reason it's useful is because there is very little that is not moving around. You can put something on the ground in front of you and call it stationary, but the ground is on a rotating planet which is orbiting a sun in a spinning galaxy. And if you want to be really accurate, you need to account for all this motion that is going on in your so-called stationary object. That's where fictitious forces come in.

They're called 'fictitious' forces to distinguish them from real forces that are always present like the electromagnetic force. A fictitious force is only present when you are in a specific frame of reference.

Perhaps the best known one is centrifugal force. If you spin a bucket of water around your head, the water doesn't fall out even when the bucket is upside down. From a certain point of view, there would seem to be something 'holding' the water in the bucket, and that fictional force is the centrifugal force. From another point of view, the water is held in the bucket because of inertia. It wants to keep moving in a straight line, but is constrained by your pulling on the string.

Another good example is coriolis force - what supposedly causes water to swirl in one way down a drain and deflects the paths of hurricanes from straight lines to curved ones. The coriolis force is caused by the rotation of the Earth. If you were in space, you wouldn't observe this force at all... even those hurricanes would seem to move in straight lines. If you're on a specific patch of earth, however, what was a straight line in space LOOKS curved to you.

It's sometimes a difficult idea to wrap your head around. Follow the link... there's a good animated picture there. One of Einstein's revelations is that even gravity is a fictional force because you can choose a reference frame where it disappears. But that's another discussion!

Answer 2

A fictitious force is an apparent force that acts on all masses in a non-inertial frame of reference, e.g., a rotating reference frame. The force F does not arise from any physical interaction, but rather from the acceleration a of the non-inertial reference frame itself. Due to Newton's second law F = ma, fictitious forces are always proportional to the mass m being acted upon

Answer 3

A fictitious force is a non existent force that is created to help explain ideas or help solve physical problems. An example is centrifugal or centripetal forces.