Angular momentum finding the principle axis

In summary, when trying to find the angular momentum about the mass centre of a rotating object, you must consider whether the axis of rotation is also rotating. Every axis of symmetry is a principal axis and to find the angular momentum, the angular velocity must be multiplied by the moment of inertia if it is along a principal axis or the tensor method must be used if not.
  • #1
SpartanG345
70
1
If an object is rotating about the axis of symmetry
and you are trying to find the angular momentum about the mass centre g.

Does a rotation about the axis of symmetry correspond to a rotation about the principle axis?
Untitled-7.jpg


For this question i am trying to find the angular momentum about the mass centre of cone which is rotating about its axis of symmetry. However the axis of rotation is also rotating about the z axis.

Does the angular velocity w effect the angular momentum about the mass centre? I am guessing it would...

The only thing i am not sure about weather or not angular momentum about G would be evaluated about the principle axis
 
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  • #2
Hi SpartanG345! :smile:

(btw, it's principal axis, like the principal of your school :wink:)
SpartanG345 said:
For this question i am trying to find the angular momentum about the mass centre of cone which is rotating about its axis of symmetry. However the axis of rotation is also rotating about the z axis.

Every axis of symmetry is a principal axis.

The principal axes of a cone are its centre line, and every direction perpendicular to that line.

To find the angular momentum, you must first find the angular velocity …

if that is along a principal axis, then just multiply by the moment of inertia; if not, then use the tensor method. :wink:
 

1. What is angular momentum and why is it important?

Angular momentum is a physical quantity that describes the rotational motion of an object. It is important because it helps us understand and predict the behavior of rotating objects, such as planets, atoms, and even subatomic particles.

2. How is angular momentum calculated?

Angular momentum is calculated by multiplying the moment of inertia, which is a measure of an object's resistance to rotational motion, by the angular velocity, which is the rate at which the object is rotating.

3. What is the principle axis of rotation?

The principle axis of rotation is an imaginary line through an object that passes through its center of mass and around which the object will rotate with the least amount of resistance. It is also known as the axis of symmetry.

4. How do you find the principle axis of rotation?

The principle axis of rotation can be found by calculating the moment of inertia of an object for different axes and then determining the axis with the lowest moment of inertia. This axis will be the principle axis of rotation.

5. What is the significance of finding the principle axis of rotation?

Finding the principle axis of rotation allows us to accurately describe the rotational motion of an object and make predictions about its behavior. It also helps us understand the symmetry and stability of an object. In many cases, the principle axis of rotation is also the axis of rotation that an object will naturally rotate around.

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