Measure the max angle of a 3D pendulum

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Discussion Overview

The discussion revolves around methods to measure the maximum angle or vertical displacement of a 3D pendulum subjected to random impacts. Various approaches are proposed, focusing on both high-tech and low-tech solutions.

Discussion Character

  • Exploratory, Technical explanation, Experimental/applied

Main Points Raised

  • One participant suggests using a high-cost 3-D camera measurement system, contrasting it with a simple method involving a hand and tape measure.
  • Another participant proposes a method involving a radial array of flat rulers placed on a table, where the distance pushed by the pendulum rope can be used to calculate the angle using trigonometric functions.
  • A different approach involves using a common video camera to capture the pendulum's motion, recommending the use of a patterned screen for easier calculations, and suggesting that two cameras positioned at right angles could enhance accuracy.

Areas of Agreement / Disagreement

Participants present multiple competing views on measurement methods, with no consensus on a single best approach.

Contextual Notes

Some methods may depend on specific conditions such as the accuracy required, the environment of the experiment, and the available equipment.

Who May Find This Useful

Individuals interested in experimental physics, engineering applications, or those looking for practical measurement techniques for pendulum systems.

cuallito
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Hi, I need a simple way to measure the maximum angle/vertical displacement of a 3D pendulum (weight hanging from a rope) undergoing random impacts. What will work?
 
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Whelp, you could buy a $50,000 3-D camera measurement system and software, or you could use your hand and a tape measure. What's your pleasure?
 
Let the rope pass through a hole in a table. Place a radial array of flat rulers on the table. They will be pushed away by the pendulum rope. Read the distance they are pushed, with y = height of fulcrum above the table, and x = maximum push of ruler, theta = Atan( x / y ).

See; https://en.wikipedia.org/wiki/Ballistic_pendulum
 
You could use a common video camera. It won't be as accurate as a true high speed camera, but it should suffice for experimental purposes. Mount the camera in front of the pendulum at the height of the pendulum at rest. Put a screen behind the pendulum with a pattern of squares on it. Place the screen the same distance from the pendulum as the camera (makes calculating height and swing easier). Even better, two cameras and two screens at 90 deg. from each other.
 

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