Calculating Pressure for a Moving Part: 285 RPMs on a 4 Inch Cylinder

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Discussion Overview

The discussion revolves around calculating the pressure exerted on a moving part that weighs approximately 1/2 ounce and spins at 285 RPM around a 4-inch cylinder. Participants explore the necessary formulas and conversions required to determine the force and subsequently the pressure related to this scenario.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • RanMan seeks assistance in calculating the pressure on a moving part, indicating a lack of knowledge in physics and requesting a formula for the calculation.
  • One participant suggests using the formula F = Mv²/r, where M is mass, v is velocity, and r is the radius, and emphasizes the need to convert ounces to mass units and calculate velocity based on RPM.
  • RanMan expresses uncertainty about converting ounces to mass and determining velocity, reiterating the need for the force value.
  • Another participant provides detailed calculations, explaining the conversion of mass from ounces to slugs, calculating the circumference of the cylinder, and deriving the velocity from the RPM, ultimately suggesting how to use these values in the force formula.

Areas of Agreement / Disagreement

Participants generally agree on the need for specific conversions and calculations to determine the force, but there is no consensus on the final pressure calculation or the interpretation of the results.

Contextual Notes

There are limitations regarding the assumptions made in the calculations, such as the choice of units and the specific formulas used. The discussion does not resolve the final pressure calculation or clarify all mathematical steps involved.

Who May Find This Useful

This discussion may be useful for individuals interested in basic physics calculations, particularly those involving rotational motion and force calculations in mechanical systems.

RanMan
I am currently try to figure out the amount of pressure on a moving part that weights about an 1/2 oz. It spins at a rate of 285 rpms around the outside of a 4 inch cylinder.
I'm sure there has to be a formula of some sort that can assist in this calculation. Thanks for any help you may be able to give.

Thanks,
RanMan
www.prewettmills.com[/URL]
 
Last edited by a moderator:
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F= Mv²/r

where M is the mass of the object,

v is it's velocity

r the radius

You'll have to convert oz to mass units and find the object's velocity from the radius and rpm.
 
Janus, I appoligize for the detailed questions but I know absolutely nothing about physics.
I do not know how to determine the velocity nor do I know how to convert ounces to mass. I'm sorry for not knowing a thing about physics.
All I know is the information that i need which is the force.

Thanks,
RanMan
www.prewettmills.com[/URL]
 
Last edited by a moderator:
Well the unit of mass in the FPS system is the slug, and a one slug mass would weigh 32.175 lbs, and there are 16 ounces to a lb.

so mass = 1/(32.175x16)/2 = .0009625 slug.

The circumfernce of a circle of radius 4 in. is 2*4* pi = 25.13 in. or 2.094 ft.

This is the distance the object travels in one revolution. it does this 285 times per min, so its velocity is 2.094*285 = 596.79 ft/min.

divide this by 60 to get ft/sec for 9.9465 ft/sec and you have v

thus
r = .33333 ft
M= .0009625 slugs
v= 9.9465 ft/sec

plug them into the formula, and you'll get the force in pounds.
 

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