- #1
fog37
- 1,569
- 108
Hello,
A force couple is compose of two forces of equal magnitude, opposite direction and parallel lines of actions separated by a distance ##d##. The moment due to a force couple is called a pure moment because its value does not depend on the point about which the moment is computed. The force couple can be moved anywhere and its value and physical effect on the body will remain the same.
A force couple only causes a rotation of the rigid body (not a translation). About which point ##P## does the body rotation happen? Is the center of mass? If so, why? Is there a mathematical derivation? In the past, I realized that the concept of rotation is somewhat arbitrary in the sense that we can see an object rotate about different points (for ex., a free rigid body rotating/spinning in the air does not objectively rotate about the CM; it is just a mathematical convenience).
Thank you,
Fog37
A force couple is compose of two forces of equal magnitude, opposite direction and parallel lines of actions separated by a distance ##d##. The moment due to a force couple is called a pure moment because its value does not depend on the point about which the moment is computed. The force couple can be moved anywhere and its value and physical effect on the body will remain the same.
A force couple only causes a rotation of the rigid body (not a translation). About which point ##P## does the body rotation happen? Is the center of mass? If so, why? Is there a mathematical derivation? In the past, I realized that the concept of rotation is somewhat arbitrary in the sense that we can see an object rotate about different points (for ex., a free rigid body rotating/spinning in the air does not objectively rotate about the CM; it is just a mathematical convenience).
Thank you,
Fog37