What is the actual definition of rotational motion?

In summary, rotational motion refers to the spinning or rotating movement of an object around a fixed axis. This is a special case of rotational motion, as the general case involves the axis of rotation itself translating or rotating in relation to another reference. A free object does not necessarily rotate around a fixed axis, as its angular momentum and velocity may point in different directions. This can result in tumbling or rolling without slipping, as described by Goldstein in his text on Classical Mechanics.
  • #1
influx
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Ok so I roughly know what rotational motion is (e.g. the spinning of a DVD) but I wish to know the textbook definition for it. I tried Googling it but to no avail. The first link on Google gives this:

Rotation around a fixed axis is a special case of rotational motion

http://en.wikipedia.org/wiki/Rotation_around_a_fixed_axis

But as mentioned above, that is a special case only, so what is a general case of rotational motion? IE is there a definition for it?

Thanks
 
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  • #2
The general case is where the axis of rotation itself may be translating or rotating w.r.t. another reference.
 
  • #3
A free object does not in general rotate about a fixed axis. The object's angular momentum will be constant if no external torques are exerted on the object, but even that does not mean that it will rotate about a fixed axis. Angular momentum and angular velocity will point in different directions if the instantaneous rotation is not about one of the object's principal axes. The object will tumble. Or, as Goldstein puts it in his text Classical Mechanics, "The polhode rolls without slipping on the herpolhode lying in the invariant plane."
 

FAQ: What is the actual definition of rotational motion?

What is rotational motion?

Rotational motion is a type of motion in which an object rotates or spins around a fixed axis. This can occur in a circular or curved path, and the object maintains a constant distance from the axis of rotation.

What is the difference between rotational motion and translational motion?

The main difference between rotational and translational motion is the type of movement. Rotational motion involves rotation around a fixed axis, while translational motion involves movement in a straight line without any rotation.

How is rotational motion measured?

Rotational motion is typically measured in terms of angular velocity, which is the rate of change of angular displacement. This can be measured in radians per second or degrees per second.

What causes rotational motion?

The main cause of rotational motion is a torque, which is a force applied at a distance from the axis of rotation. This force creates a rotational acceleration that causes the object to spin around the axis.

What are some real-life examples of rotational motion?

There are many examples of rotational motion in our daily lives, such as the rotation of the Earth around its axis, the spinning of a top, the rotation of a ceiling fan, and the turning of a steering wheel. Additionally, many machines and tools, such as drills, gears, and turbines, rely on rotational motion to function.

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