The discussion revolves around whether a closed system can change the position of its center of mass (COM) without external forces acting on it. Participants explore the implications of internal forces and the definitions of closed systems in the context of physics.
Participants express differing views on whether a closed system can change its center of mass without external forces. There is no consensus, as multiple competing perspectives are presented regarding the role of internal forces and the definition of a closed system.
The discussion highlights the ambiguity surrounding the definitions of closed systems and internal versus external forces, as well as the implications of considering exhausted fuel in the system.
That's better. If there's no external force on a system, its center of mass will move with constant velocity.Mohammad_93 said:hmmmmm
I'd better have said "...change the velocity of its center of mass..."
Mohammad_93 said:Hello,
Can a closed system change the position of its center of mass if no external force is exerted on it?
No. The center of mass of the system--including the exhausted fuel--remains moving with constant velocity.pallidin said:Yes. BUT, an internal force must be destructive in effect in order to work.
This violates nothing, as energy is required and expended.
Think of a rocket with side thrusters.
There is no external force. The center of mass changes.
Doc Al said:No. The center of mass of the system--including the exhausted fuel--remains moving with constant velocity.
If you regard the fuel as not being part of the system, then the force it exerts is an external force.pallidin said:However, exhausted fuel is often conventionally regarded as not being a current part of the system at some point.
"Collectively" definitely yes, but with separation, other, effective aspects arise, including COM changes in the primary mass system.
Doc Al said:If you regard the fuel as not being part of the system, then the force it exerts is an external force.
Reread the question that started this thread:pallidin said:Doc, you're missing the point.
Internal explosion CAN create off-centered mass.
That the "total system" is centered is NOT the issue here.
What is the issue is that the primary mass system changes.
That's the point.
Seems pretty clear to me that the 'total system' is exactly the issue.Mohammad_93 said:Can a closed system change the position of its center of mass if no external force is exerted on it?