- #51
- 23
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This is easily summarized, in the absence of gravity, any external force on a body has the effect of translating the center of mass and rotating about the center of mass. As near a planet you cannot avoid the force of gravity, it causes the resulting force in the same way and one moment, de say the objects will rotate with respect to the center of gravity, because in small objects, it practically coincides with the center of mass. Always the GC of a gravitationally stable object is closer to the earth (in this case) than the MC.
When external forces act, they are distributed on the surface of the object, we can then add (integrate) all these forces to find a resultant, which will have the same effect, moving the MC and rotating on it. But as I said, you cannot avoid gravity, so only if the GC is displaced an appreciable distance from the MC, it will create a torsional moment trying to regain the previous stability.
The answer about which point broken is the MC.
If the density of the object is constant the MC coincides with the barycenter.
If the gravitational field is constant, the MC coincides with the GC, as no gravitational field is constant with the distance to the earth, then all stable objects have the GC lower than the MC, (it is a real but depreciable distance).
As long as the resultant of external forces (thrust, friction, etc.) passes through the same line of action as the resultant of gravity, then the object is translated in that frame of reference.
But if, in addition, the resultant of the external forces does not pass through the MC, it creates a torque that may or may not find equilibrium with the couple of the force of gravity, to find a new stable equilibrium or rotate with respect to the MC.
When external forces act, they are distributed on the surface of the object, we can then add (integrate) all these forces to find a resultant, which will have the same effect, moving the MC and rotating on it. But as I said, you cannot avoid gravity, so only if the GC is displaced an appreciable distance from the MC, it will create a torsional moment trying to regain the previous stability.
The answer about which point broken is the MC.
If the density of the object is constant the MC coincides with the barycenter.
If the gravitational field is constant, the MC coincides with the GC, as no gravitational field is constant with the distance to the earth, then all stable objects have the GC lower than the MC, (it is a real but depreciable distance).
As long as the resultant of external forces (thrust, friction, etc.) passes through the same line of action as the resultant of gravity, then the object is translated in that frame of reference.
But if, in addition, the resultant of the external forces does not pass through the MC, it creates a torque that may or may not find equilibrium with the couple of the force of gravity, to find a new stable equilibrium or rotate with respect to the MC.