Angular Momentum of a conical pendulum

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SUMMARY

The discussion focuses on calculating the angular momentum of a conical pendulum, specifically a metallic bob suspended by a thread. The parameters provided include a string length of 2.8m, a vertical angle of 21 degrees, and a bob mass of 2.9kg. The participant calculated the angular velocity as 1.936 rad/s but encountered issues with the moment of inertia calculation, mistakenly using the radius instead of the correct formula. The correct approach involves using the radius derived from the angle and string length.

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  • Understanding of angular momentum and moment of inertia
  • Familiarity with conical pendulum dynamics
  • Knowledge of trigonometric functions related to angles
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Homework Statement



A small metallic bob is suspended from the ceiling by a thread of negligible mass. The ball is then set in motion in a horizontal circle so that the thread describes a cone.
Given: Length of string = 2.8m
Angle between string and vertical: 21 degrees
Mass of bob: 2.9kg

Homework Equations



I = mr^2
w = square root of [g/(lcos(theta)]
Momentum = I x w

The Attempt at a Solution



I first calculated the angular velocity by plugging numerical values into the equation and got 1.936 rad/s. Then, I found out the moment of inertia of the bob by multiplying 2.9 x 2.8^2 [this is the step I'm not sure of], but the answer wasn't right. Is there something I missed out?
Thank you for your help!
 
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The raidus is wrong. It should be r * theta
 

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