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What provides the most friction on your average full-sized SUV?
The air or the road?
The air or the road?
tuc biscuit
New member
air I would say, double it with a poorly loaded roof rack
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Naw, a bunch of us are arguing it in the office.
Just wanted the layman's input.
Just wanted the layman's input.
vixenbabe said:
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The Shadow
Guest
DEPENDS...on aerodynamics of suv, whethert the tires are under-inflated...etc
plornive
New member
The road.
Air resistance is not proportional to weight, so the momentum would at least partially make up for the putatively greater air resistance of an SUV.
Wheels are bigger too, which I would guess would make the rotationally tangential component of friction of the road less relevant, but the wheels are bigger and the vehicle is heavy which might increase the degree of that component by contorting the surface of the tire.
I think an SUV in air at 60 MPH would go a bit of a longer horizontal distance than an SUV rolling at 60 MPH in a vacuum over an average road. That also brings to mind the conditions of the road. A very tit-smooth buttery highway may change things.
Air resistance is not proportional to weight, so the momentum would at least partially make up for the putatively greater air resistance of an SUV.
Wheels are bigger too, which I would guess would make the rotationally tangential component of friction of the road less relevant, but the wheels are bigger and the vehicle is heavy which might increase the degree of that component by contorting the surface of the tire.
I think an SUV in air at 60 MPH would go a bit of a longer horizontal distance than an SUV rolling at 60 MPH in a vacuum over an average road. That also brings to mind the conditions of the road. A very tit-smooth buttery highway may change things.
Forge
New member
By road, do you mean the friction between the tires and the road only, or do you mean the rolling friction from the entire drivetrain? The actual friction between the tires and road is small due to low surface area, where the air hits much more surface area. The actual difference between the two would depend on many things (road type, tire compound, is the car waxed?) But the rolling friction includes the gears, cams, pistons, etc. That would be much more than the air friction on the car's skin.
I am an engineer, does it show?
I am an engineer, does it show?
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We're coming up with a series of interview questions, and we all agreed that chances are, the air causes the most friction but now we're just debating on the logic of it.
We're excluding the the systemic involvement of the drivetrain.
I based my topic off your old posts vix, thanks for noticing
We're excluding the the systemic involvement of the drivetrain.
I based my topic off your old posts vix, thanks for noticing
Forge said:By road, do you mean the friction between the tires and the road only, or do you mean the rolling friction from the entire drivetrain? The actual friction between the tires and road is small due to low surface area, where the air hits much more surface area. The actual difference between the two would depend on many things (road type, tire compound, is the car waxed?) But the rolling friction includes the gears, cams, pistons, etc. That would be much more than the air friction on the car's skin.
I am an engineer, does it show?
plornive
New member
I assumed that when coasting those factors don't come into play. Also, what does surface area have to do with the friction of the wheels?Forge said:By road, do you mean the friction between the tires and the road only, or do you mean the rolling friction from the entire drivetrain? The actual friction between the tires and road is small due to low surface area, where the air hits much more surface area. The actual difference between the two would depend on many things (road type, tire compound, is the car waxed?) But the rolling friction includes the gears, cams, pistons, etc. That would be much more than the air friction on the car's skin.
I am an engineer, does it show?
GoldenDelicious
New member
i would say air.
i think that ultimately it will come down to an academic assessment of the aerodynamics of the vehicle versus the friction between rubber and road, which i suppose you could go about estimating by looking at the weight of the vehicle, the pressure on the tyre footprint, and the degree of conformation the rubber would take onto the road surface.
i think youre going to have to define a few parameters first, youre being a bit loose with what youre actually asking imo.
i think that ultimately it will come down to an academic assessment of the aerodynamics of the vehicle versus the friction between rubber and road, which i suppose you could go about estimating by looking at the weight of the vehicle, the pressure on the tyre footprint, and the degree of conformation the rubber would take onto the road surface.
i think youre going to have to define a few parameters first, youre being a bit loose with what youre actually asking imo.
Forge
New member
Also keep in mind that the speed of the suv is a huge factor here. At low speeds the friction on the tires will be much greater than the air on the body, but as the suv speeds up the air will start to overcome the tires. If it goes fast enough, the air friction force could actually become greater than the tire force.
Friction force = coeffecient of friction * working force (weight in most cases)
At low speeds the weight of the suv is much greater than the force of the air against the body. At higher speeds this changes. Ever drive a sports car really fast? It feels floaty and loose. This is what causes Nascar vehicles to lose traction and crash when bumped at high speeds, the little nudge is all that is needed to overcome the friction force of the tires, because the air against the body is already close to overcoming the tires.
Friction force = coeffecient of friction * working force (weight in most cases)
At low speeds the weight of the suv is much greater than the force of the air against the body. At higher speeds this changes. Ever drive a sports car really fast? It feels floaty and loose. This is what causes Nascar vehicles to lose traction and crash when bumped at high speeds, the little nudge is all that is needed to overcome the friction force of the tires, because the air against the body is already close to overcoming the tires.
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I think, universally, here at the office, we're thinking at around 65-70mph.
I'm more interested in the thought process for the answers candidates will be giving.
So the question will likely be phrased, "For a Ford Excursion, traveling down the highway at ~70mph, which causes the most friction; the surface of the road meeting the tires or the air meeting the surface of the vehicle?"
Sumpin like that.
I'm more interested in the thought process for the answers candidates will be giving.
So the question will likely be phrased, "For a Ford Excursion, traveling down the highway at ~70mph, which causes the most friction; the surface of the road meeting the tires or the air meeting the surface of the vehicle?"
Sumpin like that.
Forge said:
Robert Jan
New member
Depends how fast you are going.
On a normal bicycle in normal clothing the point where roll/mechanic friction is smaller than air resistance lies around 4.45 meters per second.
I imagine this speed is some higher on an SUV.
The question is flawed btw the road's friction is not limiting the cars speed or acceleration, more like the friction of the cars parts on each other
On a normal bicycle in normal clothing the point where roll/mechanic friction is smaller than air resistance lies around 4.45 meters per second.
I imagine this speed is some higher on an SUV.
The question is flawed btw the road's friction is not limiting the cars speed or acceleration, more like the friction of the cars parts on each other
The word friction comes from the Latin word frictio, from fricare to rub; akin to Latin friare to crumble, and perhaps to Sanskrit bhrInanti they injure.
From that, I get, between the body of the SUV and the tires on the road, the tires are the first to be damaged from friction. So they, the tires, have more.
From that, I get, between the body of the SUV and the tires on the road, the tires are the first to be damaged from friction. So they, the tires, have more.
Razorguns
Well-known member
>NOt a good example.
I seem to see NASA drive around buggy's on the moon back in the 60s.
Fine, let's do a plane tiwht a LOT of gravity and dense air. Take a bet on how much gasoline and power it would require to move that vehicle.
If the road had that much friction and that friction had such an impact on it's performance -- then would could surmise that a ferrari culd go faster if it had smaller and thinner tires no?
Last time I also checked -- indy cars had very aerodynamic bodies, yet big ass huge tires. I guess it proves what the indy car engineers were more concerned with right there.
I seem to see NASA drive around buggy's on the moon back in the 60s.
Fine, let's do a plane tiwht a LOT of gravity and dense air. Take a bet on how much gasoline and power it would require to move that vehicle.
If the road had that much friction and that friction had such an impact on it's performance -- then would could surmise that a ferrari culd go faster if it had smaller and thinner tires no?
Last time I also checked -- indy cars had very aerodynamic bodies, yet big ass huge tires. I guess it proves what the indy car engineers were more concerned with right there.
Razorguns said:
Dude they WANT lots of friction between the tires and the roads for transfering power to the road, braking, handling/steering, etc....
they have an engine to supply power and over come the friction... it is not an issue...
this supposed SUV does not...
supersizeme
New member
Remind me never to interview at your company. Are you trying fill your vacant God position or what is this for?
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It's for a researcher, layer 2 networking.
The interest won't be in the answer, but rather the thought process involved in coming to the conclusion.
The interest won't be in the answer, but rather the thought process involved in coming to the conclusion.
supersizeme said:
supersizeme
New member
If I answered the question by blurting out "Doom 3!!" after several minutes of deep, intense thought highlighted by me repeatedly sliding your coffee mug across the table would you say my chances of getting the job would be good or gooder.
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Goodest.
supersizeme said:
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I've compiled a pretty nasty couple pages of questions.
I like to make an interview more about finding out how the person thinks and solves problems as opposed to stupid shit like "Whats your best/worst quality" type trash.
I wanna see the person think, work through problems and accomplish something.
I like to make an interview more about finding out how the person thinks and solves problems as opposed to stupid shit like "Whats your best/worst quality" type trash.
I wanna see the person think, work through problems and accomplish something.
WODIN said:
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