Arbitrary value of the moment of a force

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    Force Moment Value
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SUMMARY

The moment of a force ##F## is determined by three factors: the force magnitude ##|F|##, the choice of the moment reference point ##P##, and the distance from point ##P## to the point of application of the force ##Q##. An object subjected to a single force will experience varying moments depending on the reference point, yet it will exhibit a consistent physical response characterized by rotation and translation. The relationship between linear momentum and angular momentum is contingent upon the reference point, with torque also varying based on this choice. Ultimately, the rate of change in angular momentum remains constant, aligning with the applied torque regardless of the reference point's location.

PREREQUISITES
  • Understanding of force magnitude and its representation as ##|F|##
  • Familiarity with the concept of moment reference points in physics
  • Knowledge of torque and its dependence on reference points
  • Basic grasp of angular momentum and its relationship to linear momentum
NEXT STEPS
  • Study the principles of torque and its calculation in different reference frames
  • Explore the relationship between linear and angular momentum in detail
  • Investigate the effects of moment of inertia on rotational motion
  • Learn about the conservation of angular momentum in various physical systems
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Physics students, mechanical engineers, and professionals involved in dynamics and rotational motion analysis will benefit from this discussion.

fog37
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Hello,
It is well know that the moment of a force ##F## depends on:
a) the force magnitude ##|F|##
b) the choice of the moment reference point ##P##
c) the distance (lever arm) from the point ##P## to the point of application of the force ##Q##.

That said, an object with a single force applied to it will experience a moment which will vary in magnitude and sign with difference choices of the moment reference point ##P##. However, physically, the object will move in one specific and unique way under that same force (rotation+translation). How do different values of the moment ##M## produce the same physical situation?

Maybe all angular quantities, like angle, angular velocity, angular acceleration, moment of inertia, rotational kinetic energy, etc. must be referred to that specific and arbitrarily chosen point ##P##?

In general, we refer vectorial quantities (position, velocity, acceleration) to the origin ##O## of the triad of Cartesian axes...
 
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fog37 said:
Hello,
It is well know that the moment of a force ##F## depends on:
a) the force magnitude ##|F|##
b) the choice of the moment reference point ##P##
c) the distance (lever arm) from the point ##P## to the point of application of the force ##Q##.

That said, an object with a single force applied to it will experience a moment which will vary in magnitude and sign with difference choices of the moment reference point ##P##. However, physically, the object will move in one specific and unique way under that same force (rotation+translation). How do different values of the moment ##M## produce the same physical situation?
The same linear momentum counts as a different amount of angular momentum depending on the location of the reference point.
The same linear force counts a a different amount of torque depending on the location of the reference point.

The two effects match so that no matter where you choose to put the reference point, the rate of change in angular momentum will match the applied torque. Moving the reference point simply gives a different set of coordinates to describe the same physical reality.
 

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