Pendulum measuring the restorative force HELP

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SUMMARY

The discussion focuses on deriving an expression for mass in a pendulum system where a force meter is used to measure the restorative force. The key equations involved are Fg = -mg, (Fg)r = -mgcos(theta), and (Fg)t = -mgsin(theta). The user initially struggles with the concept that mass does not affect the pendulum's motion, but ultimately understands that the radial force due to gravity is balanced by the tension in the string, while the tangential force is unbalanced and drives the pendulum back to equilibrium.

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milk242
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Pendulum measuring the restorative force HELP!

Homework Statement


A pendulum with length L is suspended at an angle theta. At the bottom of the pendulum, a string is attached to force meter. The string attached to the force meter is perpendicular to the pendulum string. In terms of F and theta, find an expression for mass.

Homework Equations


Fg= -mg
(Fg)r = -mgcos(theta)
(Fg)t = -mgsin(theta)

The Attempt at a Solution


What I get is all the tangential and radial components cancel out equally zero, which I would expect because mass doesn't matter in a pendulum. So I don't understand how I'm suppose to obtain an expression for mass.
 

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Hi milk242, welcome to PF.
Radial force due to mg is balance by the tension in the string. Where as the tangential force is an unbalanced force which tries to bring the bob to the equilibrium position.
Your force meter measures this force, which is perpendicular to the string.
 


Thanks for your help! I got it now.
 

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