Mass and Force 4

[vagulus]

I always get confused. It's never gone away.

Assume I have a piston 170mm dia. in a vertical cylinder.
Assume zero friction.
Assume perfect seal.
What must the piston weigh to maintain a pressure of 0.1Bar in the cylinder?

(You wouldn't believe the variety of answers I have calculated! )

----------------------------------------
Artificial Intelligence is no match for Natural Stupidity

 

[3DDave]

Convert Bar to N/mm^2 then multiply by the area in mm^2 to get Newtons.

 

[robyengIT]

same as 3DDave but thought in an other way. what is the weight that a pressure of 0.1 bar can keep lifted ?

 

[vagulus]

Here's where the confusion starts!

Perhaps I should have asked what must be the mass of the piston to maintain a pressure of 0.1Bar in the cylinder. What I am after is a figure in kilograms.

Thanks



----------------------------------------
Artificial Intelligence is no match for Natural Stupidity

 

[MintJulep]

Mass and weight are related by the gravitational constant of whatever planet you are confused on.

 

[3DDave]

The mass depends on the acceleration - usually the gravitational constant, but if the item is on a bumpy flight or a rocket then that may change the amount.

 

[HTURKAK]

Pressure = F/ A = ( Wt of piston )/( Area of piston )

0.1 Bar =0.01 N/mm2

0.01= W/ (0.25*170^2 *pi)

W=0.01 * (0.25*170^2 *pi)

W= 227 N = 23.1 kg ( kgf) = 51 lb

 

[LittleInch]

Pressure = Force / Area.

So find the force.

I'll do it in m

1 bar = 100,000KPa or N/mm2
0.1 = 10,000 N/mm2
Area of piston = Pi R^2 = 3.14159 x (0.085^2) = 0.0227 m2
Force = 10,000 * 0.0227 = 227N - SNAP

Now force in a vertical plane on the earths surface = mass x gravity

So mass = 227 /9.81 = 23.1 kg



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

Weight is a force caused by gravity acting upon a mass. Weight changes on different planets. You can be weightless but not "massless".

 

[TheTick]

The mass depends on the acceleration - usually the gravitational constant, but if the item is on a bumpy flight or a rocket then that may change the amount.

I'm going to assume a minor mental flip-flop that happens to us all, rather than jump on you with a terse "WRONG".

Mass is constant. Whether floating in zero G or deep in the core of the earth, a gram of mass is a gram of mass (excluding relativistic effects not applicable here). Reduced to first principles, mass is an expression of the number and atomic mass of atoms present in an object.

Weight is a force: w=mg; g=9.81 ms². Balance the forces. Then figure out mass required to attain desired weight force.

p.s. internet life hack: To get an answer to a question, have someone post a wrong answer, and someone will come correct it in short order.

 

[3DDave]

The required mass, which is the question. No mental flip-flop on this side of the room.

 

[vagulus]

Thanks folks. At least two of my calculations gave me the right answer. I just refused to believe it. No wonder you can generate so much force with hydraulics with relatively little pressure.

----------------------------------------
Artificial Intelligence is no match for Natural Stupidity

 

[LittleInch]

Yup. A 170mm diam piston is pretty big.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[3DDave]

Is 170mm the size of a banana? I think we need to have a banana for scale.

 

[IRstuff]

Is 170mm the size of a banana?

Diameter, or length?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[3DDave]

Depends on how brave you are.