What is the difference between an Inertial force and non -Inertial force?

Answer 1

Some bad answers above!

Newton's F=mA is defined to be true when measured in an inertial reference frame. An inertial ref. frame is a frame that is not being accelerated in any way. This force F, is a "true" force.

A non-inertial force is sometimes called a pseudo-force. It is a force measure with respect to an accelerated ref. frame. This uses Newton's law in a situation where it shouldn't be applied to solve for the pseudo-force. This pseudo-force can be convenient.

For nearly 100 years long range Naval guns compute trajectories by estimating the effect of gravity, air resistance, as well as centrifugal and Coriolis force. The latter two forces are pseudo forces that are a convenient computation crutch that make the spinning earth behave as though it were stationary (not spinning).

If you sit in a tree and look down on a boy hanging on the outer edge of a merry-go-round, then you see the bar of the merry-go-round pushing the boy in a circle. This is a real "centripetal" force. The boy feels like there is a mysterious horizontal gravity-type force that wants to throw him outward. This is a pseudo "centrifugal" force, or non-inertial force.

Answer 2

An inertial force is a reaction to an accelerating force. Within accelerating reference frame, it appears to be a real force, but from a non-accelerating ("inertial") reference it doesn't exist.

In a rapidly accelerating vehicle, the force that you feel pushing you back in your seat is an inertial force. Although you feel it as a force, it's just your body's resistance to acceleration - your inertia. From out side the vehicle, we see the seat is applying a forward force on you and you're accelerating. Meanwhile, you experience that acceleration as a force.

Centrifugal force is also an inertial force. It's the reaction to the force required to make something turn in a circle.

Answer 3

We usually assume that our laboratory walls represent an inertial frame of reference. In fact, those walls are accelerating toward the center of the Earth, and the Earth is accelerating toward the sun. You can get closer to inertial by placing the lab on a westbound train, moving equal and opposite the Earth's rotation speed, on a perfectly circular track around the world at constant latitude. To find a truly inertial frame of reference, you must place your laboratory walls in the middle of a cosmic void where gravitational potential is constant; with no external force applied, the lab will be truly inertial. When you get to cosmological scales, a truly inertial reference frame will be affected by the expansion of space. The expansion will be equivalent to a gravity hill centered on the origin, regardless of where you place the origin. The shape of that "hill" will be parabolic until relativity comes into play. Then it takes on some kind of hyperbolic trig function shape. I'm not a mathematician, so I don't know how to calculate it. Cosmologists, prefer to use comoving coordinates instead of inertial coordinates. In comoving coordinates, relative motion due to expansion is considered to be "apparent motion" and relativity does not apply to it.

Answer 4

the presence of inertia