# Angular Momentum

The power through which an object rotates, keeping in mind the angular velocity and the inertia moment is commonly known as Angular Momentum in Physics.

Physics is used in every aspect of our lives. Think about the times when you walk. Your body moves! The motion that you have made while walking is known as Momentum in Physics. Momentum is the movement of an object concerning its mass and velocity. One can say that momentum of an object depends directly on the mass and velocity of the object. These two elements are the most important concepts of Momentum. Now, one of the most crucial questions in this concept is whether momentum is a vector quantity or scalar quantity? To answer this question, let us point out the elements needed to say that a quantity is a vector quantity- Magnitude and Direction. Any quantity that has a magnitude and a direction is a vector quantity. If we observe critically, we will find that Momentum has both a direction and a magnitude, which makes it a vector quantity.

In the below-given cases, which vehicle would have more momentum? A car moving at a fast pace or a semi-truck with furniture in the back? To answer this, we must consider the mass and velocity of the vehicle. In the carcass, since the mass is small the vehicle would stop as soon as the brakes are applied. However, in the semi-track case, the mass is high and the vehicle would take time before stopping. Therefore, we can say that the semi-track has more momentum, as compared to the car.

An important concept of Momentum is the Angular Momentum. It measures the rotation power of an object.

Let us briefly discuss the angular momentum meaning using examples.

## Angular Momentum through example

To understand the angular momentum meaning, we must first be aware of the etymology of the terms ‘Angular’ and ‘Momentum’. Angular comes from a Greek word, “Ankulus”- meaning “bent”. On the other hand, Momentum is taken from a Latin word- meaning “movement”. Therefore, the terms together may mean bending movement or rotational movement of an object.

As already mentioned, Angular Momentum states the rotational movement of an object or a body. It is an important concept in Physics and Mechanics. Just like Momentum, Angular Momentum is also a vector quantity- has both a direction and a magnitude. Let us understand this with the help of an example.

We have all seen spin-skaters skating. How do they skate? How does their body works while they skate? Often, we have seen that when the skater starts skating, their hands are far apart from their body. They use their hands to increase their velocity. They bring their hands closer to their body. Through this, their angular momentum is conserved and they can spin-skate faster at higher velocities.

The principle related to conserving Angular Momentum says that when no external force is put on an object, the object’s total angular momentum remains unchanged. This principle plays an important role in the world of mechanics. An example of conserving angular momentum can be the situation of a person who sits in a spinning chair while holding a small bicycle wheel. After a while, the person changes the direction of a spinning bicycle wheel, which eventually makes the person rotate their spinning chair- conserving angular momentum.

There are two types of Angular Momentum. These two types are- Spin and Angular Momentum. Spin momentum is the type of momentum for various objects that turns around an axis that passes through an object- an object spinning around its centre. Whereas, orbital angular momentum is the type of angular momentum which is similar to the rotation of various planets in the solar system, around the sun.

Orbital Angular Momentum seems interesting, isn’t it? Let us discuss the Orbital Angular Momentum in brief.

## Orbital Angular Momentum

As mentioned earlier, Orbital Angular Momentum is a type of Angular Momentum which depends on the shape and direction of its orbit. It is the rotation of electrons around the nucleus- just as the rotation of planets around the Sun. However, we must keep in mind that, unlike Spin Angular Momentum, in the orbital angular momentum the top of the object does not rotate.

Bohr highlights that the electrons that revolve around the nucleus are eminently quantized. He points the electrons travel to chosen orbits when the electron’s angular momentum is a fundamental product of  h/2.

### Conclusion

Momentum is the movement of an object concerning its mass and velocity. One can say that momentum of an object depends directly on the mass and velocity of the object. Momentum has both a direction and a magnitude, which makes it a vector quantity. An important concept in Physics and Mechanics, Angular Momentum is an important concept. Angular Momentum states the rotational movement of an object or a body. One principle related to Angular Momentum is the principle of conserving Angular Momentum, which says that when no external force is put on an object, the object’s total angular momentum remains unchanged. Angular Momentum is of two types- Spin and Orbital. Spin momentum is the type of momentum for various objects that turns around an axis that passes through an object. And, Orbital Angular Momentum is the rotation of electrons around the nucleus.