Rotational Motion

We're used to seeing linear motion every day in our lives. When cars go up and down the road, when planes soar up in the sky, when we move our hands to write, all of that is mainly linear motion. However, there is also motion associated with the rotation of objects. These can be exemplified by actions like when you spin a wheel, where the object isn't moving anywhere in space but rather rotating in space. This motion is due to the rotation of an object around a given axis of rotation, also known as rotational motion.

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Rotational motion is very much like linear motion as the equations that govern it are derived in very similar ways. For example, the change in angular position of an object over time is given by its angular velocity just like how the change in linear position of an object over time is its linear velocity. We definitely recommend you check out the first few sections on mechanics to understand linear motion because that is integral to understanding rotational motion.

As we mentioned before, rotational motion is very analogous in many ways and that analogy starts with the quantities that govern rotational motion, that are inherently analogous to their linear "cousins".

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One important distinction to make is that rotational motion is not the same as circular motion. An object can rotate around an internal axis of revolution(like its center of mass) or an external axis of revolution(like the Earth around the Sun) but an object in circular motion must rotate around an external axis of revolution. This also shows that circular motion is always tangentially linear while rotational motion doesn't have to be linear at all.

Here are the topics for this section:

Moment of Inertia

Angular Position, Velocity, Acceleration

Torque

Angular Energy

Rolling