Long rod rotating on frictionless surface

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SUMMARY

The discussion centers on the mechanics of a long rod rotating on a frictionless surface when a force F is applied at a distance L/4 from its center of mass. It is established that while the rod may not initially rotate about its center of mass during the application of force, it will inevitably do so once the force is removed. The torque generated by the force creates angular momentum, which dictates that the rod's rotation stabilizes around its center of mass after the external force ceases.

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  • Understanding of torque and angular momentum
  • Familiarity with Newton's laws of motion
  • Basic knowledge of rigid body dynamics
  • Concept of center of mass in physical systems
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  • Explore the concept of angular momentum conservation
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Horvath Bela
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If I take a rod of length L and lay it down on a surface with no friction and act upon it with a force F off its center of mass by let's say L/4, there will be a torque on the object and it will start to rotate around its center off mass. My question is why does the object necessarily rotate around its center of mass and not simply around some arbitrary point on its self, since I could write the torque equation for every point on the rod.
 
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Horvath Bela said:
If I take a rod of length L and lay it down on a surface with no friction and act upon it with a force F off its center of mass by let's say L/4, there will be a torque on the object and it will start to rotate around its center off mass. My question is why does the object necessarily rotate around its center of mass and not simply around some arbitrary point on its self, since I could write the torque equation for every point on the rod.
While you are applying the force, it won't necessarily rotate about its CM. After you have let go of it, it will do so. What's the difference? :smile:
 

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