OK Math Geeks, answer this!

[Big Don]

If a perfectly spherical ball is sitting on a perfectly flat surface, what is the size of the contact area?

 

[Kinghercules]

If a perfectly spherical ball is sitting on a perfectly flat surface, what is the size of the contact area?

Mathematically, the contact area is zero, and so if the ball had any mass, it would apply infinite pressure to the flat surface. The smallest possible area would be of the order of the Bohr radius squared.

 

[elder999]

Mathematically, the contact area is zero, and so if the ball had any mass, it would apply infinite pressure to the flat surface.

Contact "area" of zero, or, rather, a single point.

Undefined pressure.(Says the amateur mathemtician)

The smallest possible area would be of the order of the Bohr radius squared.

Or, "three points of contact, each one atom." (Says the reluctant physicist)

Or, the two surfaces must deform on contact, resulting in a small but definable contact area, and a large but definable pressure (says the engineer)

Or, "there's no such thing as a perfctly spherical ball or a perfectly flat surface." (Says the realist :lol

 

[Steve]

Very small says the English major.




Sent using Tapatalk. Please ignore typos.

 

[Big Don]

Or, "three points of contact, each one atom." (Says the reluctant physicist)

H2O I assume? What about the flat surface's make up?

Or, "there's no such thing as a perfctly spherical ball or a perfectly flat surface." (Says the realist :lol

Since the very idea of trying to figure this out gives me a headache, I posted it, because the smart *** prick in me, knows it will drive someone to long hours of mathematical endeavor...
That and I figured it would be good for a smart *** response from Elder, and it was totally worthwhile.

 

[Kinghercules]

Its weird to think about the illusion of any contact made and that their is really just an electrostatic repulsion between adjacent atoms of the sphere and flat surface, at the atomic level. From a quantum perspective some percentage of the contact atoms are actually simultaneously inside the surface. Beyond that its even stranger to try to wrap our heads around & try to understnd what matter really is.

 

[elder999]

Its weird to think about the illusion of any contact made and that their is really just an electrostatic repulsion between adjacent atoms of the sphere and flat surface, at the atomic
Pancake bunny.

Seriously?

From a quantum perspective some percentage of the contact atoms are actually simultaneously inside the surface. Beyond that its even stranger to try to wrap our heads around & try to understnd what matter really is.

:lfao:

This is unprecedented.

Double pancake bunny, :lfao:

 

[Kinghercules]

Lmfao!!!!!

 

[cdunn]

H2O I assume? What about the flat surface's make up?

Since the very idea of trying to figure this out gives me a headache, I posted it, because the smart *** prick in me, knows it will drive someone to long hours of mathematical endeavor...
That and I figured it would be good for a smart *** response from Elder, and it was totally worthwhile.

Water has nothing to do with it. Three points makes a plane, a functional tripod for the sphere - each atom being equidistant from the surface gives you a stable balance for the sphere, engaged with their opposites on the plane, whose number will depend on the packing coordination of the surface material. Less is possible, but distinctly less likely, else we go for a roll.

 

[Xue Sheng]

Well your all WRONG the correct answer is..... 42

 

[Big Don]

Well your all WRONG the correct answer is..... 42

No, no, no, that is the answer to life the universe and everything.

 

[Xue Sheng]

No, no, no, that is the answer to life the universe and everything.

EXACTLY....it is the answer to "everything"

 

[Carol]

pancake bunny

*deadpan*

I can see the flat surface. And I can get the idea of a round surface. But those are far from perfectly flat or perfectly round.


:lfao:

 

[Kinghercules]

Water has nothing to do with it. Three points makes a plane, a functional tripod for the sphere - each atom being equidistant from the surface gives you a stable balance for the sphere, engaged with their opposites on the plane, whose number will depend on the packing coordination of the surface material. Less is possible, but distinctly less likely, else we go for a roll.

If it were frictionless than it wouldn't roll it would glide across surface unless the initial force imparted a rolling motion.

 

[Kinghercules]

I would say that the Physicist-Engineer case here is a bit of a false dichotomy, physicists and engineers both sometimes do rigid body and sometimes deformation modeling. I should point out that you can also say that, at an atomic level, there's really no definite contact (as well as no uniform surface). There is still space between the atoms of the spherical object and those of the planar object.

 

[elder999]

I would say that the Physicist-Engineer case here is a bit of a false dichotomy, physicists and engineers both sometimes do rigid body and sometimes deformation modeling..

Well. as a nuclear and mechanical engineer with a PhD in physics, I'd say......what I said. :lol:

 

[Jenna]

If a perfectly spherical ball is sitting on a perfectly flat surface, what is the size of the contact area?

I further wonder does a perfectly spherical ball sitting on a perfectly flat surface roll around infinitely with no resistance if nobody is there to witness it?

 

[Sukerkin]

Very Zen, Jenna :lol:.