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Cavendish Gravity Experiment: How to Evaluate and Choose the Materials
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By Andrew Bennett
After learning from a few previous versions of the Cavendish gravity experiment, I am carefully examining options for my third version. In the video below, we examine some of my options for materials.
Choosing Wire with a Low Torsion Constant
The big decision I need to make is what to use as the wire that the torsional balance hangs from. Ideally, we want something with a very low torsion constant. This means that the wire presents very little resistance to twisting. Since the gravitational forces that will twist the pendulum are so small, the torque resisting that twist needs to be extremely small, as well.
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The torsion constant seems to depend both on the material the wire is made of and the diameter of the wire. In the video below, we investigate some possibilities and discuss the material and diameter of each option.
What's Next in My Cavendish Demo Project?
I still have a question about whether the length of the wire will affect this quantity. In the next video, I'll use a torsional pendulum to determine the torsion constant of each wire. I'll also experiment to see if the length of the wire affects the constant.
What Do You Think?
Which wire type will have the lowest constant and why? Do you think the length matters? Why or why not?
To stay in the loop on this project, make sure to subscribe to this blog and my YouTube channel. That way, you'll get email alerts when updates are available.
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YouTube Screenshot ( https://www.youtube.com/watch?v=19QbqZjKqJQ ) By Andrew Bennett Gravity Demo 3.0 Is Underway This video marks the beginning of my third dive into the Cavendish experiment . Before now, I've created devices that could potentially show the effects of gravitation between small objects. However, I have never eliminated enough sources of uncertainty to make that definitive or to derive a value for G. That is the goal of this summer's physics project. Math Behind Cavendish Experiment Explained In this video, I work through the math for determining G from the Cavendish gravity experiment. This math includes the Law of Universal Gravitation, equations for torque (from both a point force and a twisted string), the formula for the period of a torsional oscillator, and some equations for calculating rotational inertia. The end result is an ugly equation that will get us an important value: the Universal Gravitational Constant. More Info on My Newest Grav...
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