Pendulum SHM: Vector Direction of Weight vs. Tension

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    Pendulum Shm
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Discussion Overview

The discussion centers around the vector directions of forces acting on a pendulum, specifically the weight and tension, in the context of simple harmonic motion (SHM). Participants explore the nature of the restoring force and its derivation from these vectors.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why the restoring force is expressed as Fnet = mg sin θ, suggesting that the tension's contribution might also be relevant, particularly in comparison to centripetal force.
  • Another participant clarifies that the restoring force is the net force acting on the pendulum's bob, indicating that the resultant of tension and weight, when considered as vectors, leads to the magnitude of mg sin θ.
  • A request for illustrations is made to better understand the forces acting on the pendulum.
  • A later reply offers to provide illustrations by drawing the forces and analyzing their components along tangential and radial directions.

Areas of Agreement / Disagreement

Participants express differing views on the role of tension in determining the restoring force, indicating that the discussion remains contested and unresolved.

Contextual Notes

Participants have not yet provided specific illustrations or detailed mathematical derivations, and there may be assumptions regarding the definitions of forces that are not explicitly stated.

ehabmozart
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I've seen in many sites that a pendulum restoring force Fnet = mg sin theta... Why did we actually get the vector direction of the weight and not the vector of the tension.. Simply, as in centrepetal force.. It would be Tsin theta would be the net restoring force? Thanks!
 
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The restoring force is the net force acting on the pendulum's bob.
If you add the tension and the weight (as vectors) and consider inextensible suspension string the resultant is tangent to the trajectory and its magnitude is mg sinθ.
 
Can i have illustrations then??
 
Sure you can. Draw the forces acting on the pendulum and then take the components along the tangential and radial directions.
 

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