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Welcome to our Physics lesson on **Angular Momentum**, this is the fifth lesson of our suite of physics lessons covering the topic of **Dynamics of Rotational Motion**, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.

Angular momentum, L, is a vector quantity (more precisely, a pseudo-vector) that represents the product of a body's rotational inertia and rotational velocity (in radians/sec) about a particular axis. It is the equivalent of **momentum** in linear motion.

Mathematically, we can write

L = I × ω

The unit of angular momentum is [kg × m2 / s].

What is the angular momentum of Earth when revolving around itself? Take the following approximate values: MEarth = 6 × 1024 kg, REarth = 6400 km and TEarth = 86400 s.

Earth can be considered as a solid sphere. Therefore, its moment if inertia is

I = *2**/**5* m × R^{2}

We have, R = 6400 km = 6 400 000 m = 6.4 × 106 m. Also, m in the formula is replaced by M as Earth has a very large mass. Hence, we can write:

I = *2**/**5* M × R^{2}

=*2**/**5* × 6 × 10^{24} × (6.4 × 10^{6})^{2}

= 1.64 × 10^{37} kg × m^{2}

=

= 1.64 × 10

Now, let's calculate the angular velocity of Earth. Since for one revolution φ = 2π and t = T, we have

ω = *φ**/**t*

=*2π**/**T*

=*2 × 3.14 rad**/**86400 s*

= 7.27 × 10^{-5} *rad**/**s*

=

=

= 7.27 × 10

Hence, Earth's angular momentum is

L = I × ω

= 1.64 × 10^{3}7 kg × m^{2} × 7.27 × 10^{-5} *rad**/**s*

= 1.19 × 10^{3}3 *kg × m*^{2}*/**s*

= 1.64 × 10

= 1.19 × 10

You have reached the end of Physics lesson **7.2.5 Angular Momentum**. There are 8 lessons in this physics tutorial covering **Dynamics of Rotational Motion**, you can access all the lessons from this tutorial below.

Enjoy the "Angular Momentum" physics lesson? People who liked the "Dynamics of Rotational Motion lesson found the following resources useful:

- Angular Momentum Feedback. Helps other - Leave a rating for this angular momentum (see below)
- Rotation Physics tutorial: Dynamics of Rotational Motion. Read the Dynamics of Rotational Motion physics tutorial and build your physics knowledge of Rotation
- Rotation Revision Notes: Dynamics of Rotational Motion. Print the notes so you can revise the key points covered in the physics tutorial for Dynamics of Rotational Motion
- Rotation Practice Questions: Dynamics of Rotational Motion. Test and improve your knowledge of Dynamics of Rotational Motion with example questins and answers
- Check your calculations for Rotation questions with our excellent Rotation calculators which contain full equations and calculations clearly displayed line by line. See the Rotation Calculators by iCalculator™ below.
- Continuing learning rotation - read our next physics tutorial: Centripetal Force

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