eiinertiaalisuus

Eiinertiaalisuus refers to a state of not being inertial. An inertial frame of reference is one in which Newton's first law of motion holds true. This means that an object at rest will stay at rest, and an object in motion will continue in motion with the same speed and in the same direction, unless acted upon by an external force.

In contrast, a non-inertial frame of reference is one that is accelerating. In such a frame, objects may appear to accelerate even without any external forces acting upon them. This apparent acceleration is due to the acceleration of the reference frame itself. To describe motion in a non-inertial frame, fictitious forces, such as the centrifugal force and the Coriolis force, are introduced to make Newton's laws appear to hold.

For example, if you are standing on a merry-go-round that is spinning, you are in a non-inertial frame of reference. You might feel a force pushing you outwards, which is the centrifugal force. This force isn't a real force in the sense of an interaction between two objects, but rather an effect of the circular motion of your reference frame. Similarly, if you are in a car that is accelerating, you will feel pushed back into your seat. This sensation is also due to the acceleration of your frame of reference.

Understanding the difference between inertial and non-inertial frames is crucial in physics, particularly in classical mechanics and special relativity. While inertial frames are the simplest to analyze, many real-world situations involve non-inertial frames, requiring the use of fictitious forces for accurate description.