AWD??

[GoCougs]

Try it...

For the rest of us, a nail nailed into a board is held into wood by static friction.  What is harder to pry out of the board - a small finishing nail or a huge ass nail.  Of course its the huge ass nail... Yeesh

And by the way, if I am took your brick and super glued it without you knowing it, you would describe it as having a hell of a lot of friction.

Friction force is higher for the larger nail but it's not due to larger surface area; larger diameter = more compression of the wood = more normal force = more friction force.

[MX793]

Try it...

For the rest of us, a nail nailed into a board is held into wood by static friction.  What is harder to pry out of the board - a small finishing nail or a huge ass nail.  Of course its the huge ass nail... Yeesh

And by the way, if I am took your brick and super glued it without you knowing it, you would describe it as having a hell of a lot of friction.

Larger nail displaces more wood, meaning more pressure on the nail (greater force normal on the surface).  It has nothing to do with surface area.  Drive a nail 1" deep and see how much force it takes to remove it.  Then drive it in 3" and see how much force it takes to crack it loose.  It's the same.

[GoCougs]

Am I really the only one that paid attention in physics...

I was more    about the duct tape and child...

Dude, we all learned the the static friction force equation in high school:  F_f,s= μ_s * F_N

[r0tor]

Larger nail displaces more wood, meaning more pressure on the nail (greater force normal on the surface).  It has nothing to do with surface area.  Drive the same nail 1" deep and see how much force it takes to remove it.  Then drive it in 3" and see how much force it takes to crack it loose.  It's the same.

No shit Sherlock.  There is always more to the full picture when dealing with static friction.  In this case the overall friction force is dependant upon the area of the nail which displaces the wood which causes the greater force.

End of the day, you just proved that the area of the nail determined the frictional force.  Maybe not the coefficient of static friction, but the overall frictional force.

[GoCougs]

[Eye of the Tiger]

No shit Sherlock.  There is always more to the full picture when dealing with static friction.  In this case the overall friction force is dependant upon the area of the nail which displaces the wood which causes the greater force.

End of the day, you just proved that the area of the nail determined the frictional force.  Maybe not the coefficient of static friction, but the overall frictional force.

Trololololol?

[MX793]

No shit Sherlock.  There is always more to the full picture when dealing with static friction.  In this case the overall friction force is dependant upon the area of the nail which displaces the wood which causes the greater force.

End of the day, you just proved that the area of the nail determined the frictional force.  Maybe not the coefficient of static friction, but the overall frictional force.

Wat?  A nail driven 3 inches deep has more surface area in contact with the wood than when driven 1 inch deep.  Force to crack that nail lose is the same regardless of how deep it's driven into the wood.  Different surface area, same force. 

I drive a 1/8" diameter nail into a board 4" deep (1.18 in^2) and a 1/4" diameter nail 1" deep (.785 in^2), the fatter nail is still harder to crack loose.  Uh-ohs.  Less area, more friction?!  That's unpossible!

[Byteme]

No shit Sherlock.  There is always more to the full picture when dealing with static friction.  In this case the overall friction force is dependant upon the area of the nail which displaces the wood which causes the greater force.

End of the day, you just proved that the area of the nail determined the frictional force.  Maybe not the coefficient of static friction, but the overall frictional force.

I think for the nail in wood example you have two forces at work; friction which would increase as the nail's surface area (diameter for any given depth) and a clamping force as the displaced wood has a tendency to spring back to it's original position.  After all, the force required to remove the nail will vary depending what wood it's driven into.  But for any given wood a smaller diameter nail will be easier to remove (or drive for that matter).
Maybe skin friction in pilings is a better example.  IIRC,  increasing the diameter of the pile increases it's load bearing capacity. 

[r0tor]

Holy pluck... It was outlined earlier why a wider tire has more traction.  OVERALL, "FRICTION" in its static state is dependent on area.  Put away your high school equation.

[GoCougs]

Wat?  A nail driven 3 inches deep has more surface area in contact with the wood than when driven 1 inch deep.  Force to crack that nail lose is the same regardless of how deep it's driven into the wood.  Different surface area, same force. 

The nail driven 1" deep will be easier to pull out than the nail driven 3" deep. You're still correct that it has nothing to do with surface area. It's analogous to uniform beam loading; the further the nail is driven into the wood the greater the total friction force (= more displaced wood).

[MX793]

Holy pluck... It was outlined earlier why a wider tire has more traction.  OVERALL, "FRICTION" in its static state is dependent on area.  Put away your high school equation.

Show me one equation that mathematically relates friction force to surface area.  If they are co-dependent, then there is a mathematical relationship between the two.

[GoCougs]

Holy pluck... It was outlined earlier why a wider tire has more traction.  OVERALL, "FRICTION" in its static state is dependent on area.  Put away your high school equation.

You're equating/confusing friction and traction...

Even so, if you disagree with the "high school" equation for static friction, you're simply wrong.

[r0tor]

Show me one equation that mathematically relates friction force to surface area.  If they are co-dependent, then there is a mathematical relationship between the two.

Most static friction is heavily influenced by surface irregularities and interferences.  There is no reliable equation for static friction and there ie no reliable database of static friction coefficients that work in the real world.

[r0tor]

You're equating/confusing friction and traction...

Even so, if you disagree with the "high school" equation for static friction, you're simply wrong.

"Traction" was in invented when someone's high school physics equation didn't work in the real world... And I'm not he one that brought a misguided notion of friction into the thread...

[MX793]

The nail driven 1" deep will be easier to pull out than the nail driven 3" deep. You're still correct that it has nothing to do with surface area. It's analogous to uniform beam loading; the further the nail is driven into the wood the greater the total friction force (= more displaced wood).

The fatter nail displaced the greater volume of wood in this case.

[MX793]

Most static friction is heavily influenced by surface irregularities and interferences.  There is no reliable equation for static friction and there ie no reliable database of static friction coefficients that work in the real world.

If friction force it dependent on surface area, then there is a mathematical equation describing that relationship.  Show me the equation.

And there are plenty of real world scenarios where friction coefficients "work".

[r0tor]

The fatter nail displaced the greater volume of wood in this case.

It displaces the same volume per length...

[MX793]

It displaces the same volume per length...

A fatter nail displaces the same volume per length as a skinnier nail?  Now I've heard it all...

[GoCougs]

"Traction" was in invented when someone's high school physics equation didn't work in the real world... And I'm not he one that brought a misguided notion of friction into the thread...

Then why do you keep confusing the two?

Traction can be dependent on surface area. Static friction is not.

[Eye of the Tiger]

Let's talk about suspension tuning.

[r0tor]

A fatter nail displaces the same volume per length as a skinnier nail?  Now I've heard it all...

A fatter nail displaced the same amount of wood per length of the nail.  And yes, it does matter if a nail is driven 3" or 1" into something

[Eye of the Tiger]

A fatter nail displaced the same amount of wood per length of the nail.  And yes, it does matter if a nail is driven 3" or 1" into something

So much confuse. Wow.

[r0tor]

Then why do you keep confusing the two?

Traction can be dependent on surface area. Static friction is not.

Why do we need to resort to using "traction" to describe a tire holding on to a ramp covered in PE?  Oh that's right, because high school physics "friction" fails to tell the whole story.

So when someone puts his damn brick on an inclined plane, and high school physics once again fails, then all these additional forces get add into the high school physics equation to explain it.

End if the day, if something is going up a ramp like in this video or at the launching line of a drag strip... Surface area does matter.

[GoCougs]

Why do we need to resort to using "traction" to describe a tire holding on to a ramp covered in PE?  Oh that's right, because high school physics "friction" fails to tell the whole story.

So when someone puts his damn brick on an inclined plane, and high school physics once again fails, then all these additional forces get add into the high school physics equation to explain it.

End if the day, if something is going up a ramp like in this video or at the launching line of a drag strip... Surface area does matter.

So then stop using "friction" and "traction" interchangeably. Plus the brick example is correct.

[MrH]

Lol I'm starting to question if rotor really got an engineering degree. This is freshmen year, semester one stuff.

Traction and friction are two different things.

[Byteme]

A fatter nail displaced the same amount of wood per length of the nail.  And yes, it does matter if a nail is driven 3" or 1" into something

Are you saying if I drive a 1/2" diameter nail two inches into a piece of wood it would displace the same amount of wood as an 1/8th inch diameter nail driven 2" into the same piece of wood? 

[r0tor]

Lol I'm starting to question if rotor really got an engineering degree. This is freshmen year, semester one stuff.

Traction and friction are two different things.

Fine, define traction...


. The maximum value of static friction, when motion is impending, is sometimes referred to as limiting friction, [17] although this term is not used universally. [1] It is also known as traction.

Traction (engineering), adhesive friction or force

Main Entry: trac·tion Pronunciation: \ˈtrak-shən\Function: noun Etymology: Medieval Latin traction-, tractio, from Latin trahere Date: 1608 1 : the act of drawing : the state of being drawn ; also : the force exerted in drawing 2 : the drawing of a vehicle by motive power ; also : the motive power employed 3 a : the adhesive friction of a body on a surface on which it moves <the traction of a wheel on a rail> b : a pulling force exerted on a skeletal structure (as in a fracture) by means of a special device <a traction splint> ; also : a state of tension created by such a pulling force <a leg in traction>

oh fuck... traction is a frictional force and is absolutely determined by surface area

[MrH]

Traction is adhesive friction. Adhesive friction is dependent on surface area. Classic Newtonian friction is independent of surface area.

The fact you used duct tape on a ceiling as an example shows you don't understand the difference between the two.

[MX793]

Traction is limited by one of 3 factors:

The shear strength of the ground/road material
The shear strength of the tire compound
The static friction limit between the tire and the road.

The weakest link in that chain will be the cause for a loss of traction.  Sometimes it's the tire shearing on itself under the applied load, sometimes it's the ground shearing on itself under the applied load, and sometimes it's that the available frictional force limit (Cf x Fn) is less than the applied load.

Two of those are functions of surface area.  Friction force is not.

[r0tor]

Traction is adhesive friction. Adhesive friction is dependent on surface area. Classic Newtonian friction is independent of surface area.

The fact you used duct tape on a ceiling as an example shows you don't understand the difference between the two.

I don't think I ever limited myself to Newtonian friction... Which was my while point...