Question about gravitational acceleration

Click For Summary

Discussion Overview

The discussion revolves around the calculations and implications of gravitational acceleration generated by a rapidly spinning disc, specifically focusing on centripetal force, material limits, and the thermal behavior of gases in proximity to the disc. Participants explore theoretical and practical aspects of these concepts.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant questions the validity of calculated g-forces from a 1m radius disc spinning at 50,000 RPM, suggesting it may exceed those found near middle-sized stars.
  • Another participant provides the formula for centripetal acceleration and suggests converting RPM to tangential velocity to calculate g-forces.
  • A third participant discusses the relationship between energy density, tensile strength, and density of materials, indicating how these factors influence maximum tangential velocity and rotation rate.
  • Participants express uncertainty about the thermal behavior of a disc spinning in a gas chamber, questioning whether the gas behaves similarly to the solid material under rotation.
  • One participant presents calculations for force and g-forces based on a 10-meter radius disc and requests verification of their results.
  • Another participant seeks clarification on how gases or plasma respond to tangential pressure compared to solid materials.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the calculations or the thermal behavior of gases in relation to the spinning disc. Multiple competing views and uncertainties remain regarding the implications of the calculations and the physical behaviors discussed.

Contextual Notes

Participants express limitations in their calculations and understanding, particularly regarding the assumptions made about material properties and the effects of gas dynamics in the context of rapid rotation.

Who May Find This Useful

This discussion may be of interest to those studying physics, engineering, or materials science, particularly in the areas of rotational dynamics and thermodynamics.

Crazymechanic
Messages
831
Reaction score
12
not so good at math so please help me.When I play with those artificial gravity or should say centripetal force calculators I get some pretty big numbers so I need some verification of them.
Is it true that spinning a let's say 1m. radius disc with 50 000rpm/min you would get like 2795609.8954 g force on the side of the disc? And if so isn't that close or even over to that you normally would get on a middle sized star? Certainly bigger than our sun.?


How could I calculate the highest possible g force a specific flywheel or material or disc could withstand?

And the last thing a disc or whatever solid material rotating fast doesn't get very hot , well if we don't consider the air resistance and friction, but now let's imagine that around the disc is a chamber full with gas and we spin the disc very fast does the gas act similar as the solid or does the gas heat up differently?
 
Physics news on Phys.org
F = ma..right?? and for a rotating object ...a = v2/r

the v is the tangential velocity so you'll have to convert 50,000 RPM to a velocity. Each revolution travels a distance of 1 circumference or C = 2[pi]r...and you'll have 50,000 of these each minute...
How could I calculate the highest possible g force a specific flywheel or material or disc could withstand?
not likely practical to calculate it...use an experimentally determined figure:

see

http://en.wikipedia.org/wiki/Tensile_strength
 
If you look at

http://en.wikipedia.org/wiki/Flywheel_energy_storage

you can get some additional insights.

One observation is that the maximum energy density you can get is proportional to σ/ρ where σ is the tensile strength of the material and ρ is its density.

This means the the maximum tangential velocity is proportional to the square root of σ/ρ
And that means that the maximum rotation rate is roughly given by sqrt(σ/ρ)/r.
 
Thanks for the answers , oh by the way can somebody answer the last part of my thread?

And the last thing a disc or whatever solid material rotating fast doesn't get very hot , well if we don't consider the air resistance and friction, but now let's imagine that around the disc is a chamber full with gas and we spin the disc very fast does the gas act similar as the solid or does the gas heat up differently?
 
So F=ma mass let's say 5 tons and radius of the disc 10 meters. and "a" is like (assuming 50 000rpm) C = 2[pi]r that would be like 2x(3.14x10) == 2x 31.4=62.8
now a = v2/r that would mean a=62.8x62.8/10 is equal to 394.384

now the F=ma part. F=5000x 394.384= 19711920 (N)

I'm sorry for my abstract nonsense type of calculus but could someone verify that I did the calculations right?
And 19711920 N , how do I convert that to G ?

Thanks.
 
Anyone? And yes could someone tell me about how does gas or plasma states react to tangential pressure compared with a solid material?
 

Similar threads

Undergrad Integrating discs to find the gravitational force of a sphere
  • · Replies 5 ·
Replies
5
Views
4K
Undergrad Gravitational acceleration based on density
  • · Replies 11 ·
Replies
11
Views
3K
Undergrad Confusion about gravitational acceleration
  • · Replies 5 ·
Replies
5
Views
2K
High School Help Scaling Gravity Simulation
  • · Replies 7 ·
Replies
7
Views
3K
Undergrad Same old question, I still don't get it: E=1/2mv^2 - more E with V?
  • · Replies 41 ·
2
Replies
41
Views
4K
Undergrad What is the acceleration at the contact point between a wheel and surface?
  • · Replies 17 ·
Replies
17
Views
4K
Graduate Relative Centripetal Acceleration
  • · Replies 7 ·
Replies
7
Views
2K
Graduate Gravitational acceleration towards and through an object
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Relative Strength of the Magnus effect relative to gravity
  • · Replies 25 ·
Replies
25
Views
4K
Undergrad Gravitational field vs. acceleration due to gravity
  • · Replies 2 ·
Replies
2
Views
5K