Non Inertial Frames and Pseudo forces

Non inertial frame:

Definition: The frame of reference that is under acceleration or de-acceleration is known as Non Inertial Frame of Reference.

There are several ways to describe a non-inertial frame. Some of them are as follow;

A non-inertial frame of reference is a frame of reference with a changing velocity. The velocity of a frame will change if the frame speeds up, or slows down, or travels in a curved path.

A non-inertial frame of reference is an accelerating frame of reference.

A non-inertial frame of reference is a frame of reference in which the law of inertia does not hold.

A non-inertial frame of reference is a frame of reference in which Newton's laws of motion do not hold.

In a non-inertial frame of reference fictitious forces arise.

Explanation: A non-inertial frame of reference is a frame which does not have a constant velocity. When velocity is not constant so there will be acceleration or de-acceleration in that body.

In non-inertial frame of reference laws of Physics does not hold. So whenever an object whose position is judged from this frame, will seem to change its velocity continuously with no net force acting on it. This completely violates the law of inertia (Newton’s First law of motion) and Newton's laws of motion, since these laws claim that the only way an object can change its velocity is, if an actual non-zero net force is applied to the object. Objects just do not start to move about here and there all on their own. But in these frames it seems to as velocity of object is changing without application of some external force on the body. But here without any visible external force bodies start to move. To understand this we must know that what these forces are. These forces are known as pseudo forces and explain below.

pseudo forces:

Definition: The physically apparent but nonexistent force needed by an observer in a non inertial frame to make Newton's law of motion hold true is known as pseudo force. It is also known as Non-Inertial force

Explanation: It means that pseudo force is just an apparent force hat bring object to motion and these forces prove that Newton’s laws are not violated. These are hidden forces according to our supposition in Physics means they are present. If we are in a car, and suddenly the brakes are applied, then we will feel pushed toward the

front of the car or we will fell forward push. We actually have to extend our arms to prevent from going forward toward the dashboard of the car. However, there is really no force pushing us forward. The car, since it is slowing down, is a de-accelerating, or non-inertial frame of reference and the law of inertia does not hold if we use this non-inertial frame to observe our motion. If we observe that motion we will find that there is no force that is pushing us forward when the brakes are applied the car is stopping, we are not, and so to compensate this stoppage we move forward toward desk board. Actually, there is no force acting on you, but we imagined that a force act on us towards the front of car and this force is referred as pseudo force.

LIMITATIONS OF NEWTON’S LAWS

Newton's laws are applicable to macroscopic and the bodies moving with low velocity . But in case of microscopic bodies the velocity increases up to the velocity of light, and in that case the Newton’s laws becomes inapplicable. For example, when the velocity of an object is approximately equal to velocity of light, its weight can increase up to 1.7times to its original.

In the 20th century there were three revolutionary developments in physics:

1. Special theory of relativity

2. General theory of relativity

3. Quantum mechanics

According to special theory of relativity Newton’s law does not hold efficient and good. Special relativity teaches us that we cannot extrapolate the use of Newton’s laws to particles moving at speeds comparable to the speed of light. General theory of relativity shows that we cannot use Newton’s law in the vicinity of extremely massive objects.

According to Quantum mechanics Newton’s law is not good to explain the physics. Quantum mechanics teaches us that we cannot extrapolate Newton’s laws to objects as small as atoms.

On Microscopic Objects :

Newton's law are not valid in case of the microscopic objects such as electrons, proton, neutronino etc. This is because these particles have very small masses but very large velocities. When they move, they behave as wave, and Newton’s laws fail to explain the wave nature of a body. So Newton’s laws fail there.

Objects Moving with large velocities:

The Newton's law does not valid on the objects moving with large velocities approaches to the speed of light, because at large velocities the mass of the objects increases.

Another new development concerns mechanical system is described as “chaotic”. One of the hallmarks of Newton’s law is

ability to predict the future behavior of a system. Calculations combining the Newtonian’s mechanics of particles with chaos theory have shown that orbit of planet Pluto is chaotic on a timescale of ten millions of year (age of solar system=4.5 billion years; Pluto orbital speed=250 years).

Chaos theory has also been used to explain two properties of the asteroid but that cannot be understood

1. Many asteroid stray away from what should be stable orbits , some of them becoming meteorites that rain steadily down to the earth.

2. Within the asteroid belt are several empty gaps where the number of orbiting asteroid is small or zero (0). It has been only within the past decade that high speed computers have permitted detailed calculation of the dynamics of such systems to be followed for the time scales necessary to observe this unusual & as additional calculation are done, new application of this exciting field continue to be discovered.