Understanding Rigid Body Rotation: Principles and Observations

In summary, a body frame rotates with a body and does not need to be aligned with the rotation axis. The angular momentum vector is always aligned with the rotation axis and does not deviate from it. An observer on the body surface will not observe any motion on the body. The principal axis of rotation is determined by the symmetry of the body and does not necessarily need to be the rotation axis itself. In regards to point 3, if the observer is in an external static frame, they can observe the body precessing and therefore observe the existence of the angular momentum vector. Additionally, an observer can always determine the rotation of their coordinate system from the Coriolis force. There can still be principal coordinates even without evident symmetry. Finally
  • #1
Tian En
Just to confirm a few points:
  1. A body frame rotates with a body. It need not be aligned to the rotation axis.
  2. Angular momentum vector always aligned with rotation axis (not deviates from it).
  3. An observer on the body surface (body frame) observes no motion on a body.
  4. Principal axis of rotation comes from the symmetry of the body.
  5. Principal axis of rotation need not be rotation axis itself.
For point 3, is there a body angular velocity vector in the first place as observed by the observer in the body frame? I think if the observer is in the external static frame, he can then observe the body precesses and hence the existence of angular momentum vector.

Thanks.
 
Physics news on Phys.org
  • #2
An observer can always determine the rotation of his coordinate system from the Coriolis force.
 
  • #3
Tian En said:
Principal axis of rotation comes from the symmetry of the body.

There exists principal coordinates even when there is no evident symmetry.
 
  • #4
Is angular momentum vector of the rotating body precessing in the frame of an observer in the rotating body?
 

1. What is rigid body rotation?

Rigid body rotation is a type of motion in which a body maintains its shape and size while rotating around a fixed axis. This means that all points on the body move in circular paths around the axis at the same rate.

2. What are the principles of rigid body rotation?

The principles of rigid body rotation include conservation of angular momentum, moment of inertia, and angular velocity. These principles describe how the rotational motion of a rigid body is affected by external forces.

3. How is rigid body rotation different from other types of motion?

Rigid body rotation differs from other types of motion, such as translational motion, in that it involves rotation around a fixed axis instead of linear movement. In rigid body rotation, the distance between any two points on the body remains constant, whereas in translational motion, the distance between two points changes.

4. How is rigid body rotation observed in real-world scenarios?

Rigid body rotation can be observed in many real-world scenarios, such as the rotation of a spinning top, a revolving door, or the motion of a spinning wheel on an axle. It is also commonly seen in the movement of objects in space, such as planets rotating around their axis.

5. What are the practical applications of understanding rigid body rotation?

Understanding rigid body rotation is important in many fields, including engineering, physics, and astronomy. It allows us to analyze and predict the behavior of rotating objects, design efficient machines, and study the rotational motion of celestial bodies. It also has practical applications in everyday life, such as in the design of vehicles and sports equipment.

Similar threads

A Rigid body motion (RBM) transformation
    • Mechanics
Replies
3
Views
113
Rigid body kinematic motion and rotation
    • Mechanics
Replies
13
Views
2K
Does a rotating rigid body has single angular velocity.
    • Mechanics
Replies
3
Views
1K
Rotation around a non fixed axis + linear motion of a system
    • Mechanics
Replies
21
Views
2K
I Rotation about two axes and angular momentum
    • Mechanics
Replies
3
Views
918
Classical Rotation: Referencing Rotational Motion in Mechanics
    • Mechanics
Replies
5
Views
745
Rigid body with center of rotation other than CoM
    • Mechanics
Replies
15
Views
2K
KE of off-center impacts in rotating and translating rigid bodies
    • Mechanics
Replies
5
Views
916
A doubt in the rotational analogue of F=ma
    • Mechanics
Replies
3
Views
877
Projectile motion of a two-point rigid body
    • Mechanics
Replies
8
Views
1K

Hot Threads

Recent Insights

Back
Top