Weight Versus Mass

[Superman]

I suspect most of you are aware by now that Superman's brain, while not any better or more active than anyone else's, works kind of goofy. So here's my latest bonehead revelation. It seems to me that race cars are the perfect example of the distinction between mass and weight. Designers are deliberately trying to separate these two forces. In order for an F1 or Indy car to be effective, it must have as much weight as possible, but with as little mass as possible. Those things probably don't have much more than 1000 lbs of mass, but when at full speed, they push on the ground (weight) with something like 3000 or 4000 lbs.

I am assured they could race upside down, so great is the ground-effects downforce. I won't be offended if no one can get excited about this, but Superman does not have many of these revelations, so he likes to share them.

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'83 SC

[Yargk]

Yes, they could race upside down. I actually want them to. I'd pay money to see it.

Keith
79 930

[BRAINIAC]

That would make for pretty disastrous results from a stall on the upside down back straight. I think it would really make drafting whole new artform. Get it wrong and you fall head first to the ground.

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[island911]

Originally posted by BRAINIAC:
That would make for pretty disastrous results from a stall on the upside down back straight. I think it would really make drafting whole new artform. Get it wrong and you fall head first to the ground.

. . .and that is precisely why most would pay to view.

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'81 Platinum Metalic SC Coupe

[wckrause]

My old Hot Wheels could race upside down, but that was centrical force. Different concept.


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Bill Krause
'79 911SC Euro

[BRAINIAC]

Tru dat, homey. Tru dat. Island, your theory is proven by the existence of the WWF.

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Tyson Schmidt
72 911 Cabriolet
92 C-2 Cabriolet

[This message has been edited by BRAINIAC (edited 06-14-2001).]

[RarlyL8]

You could make the cars with lead tube frames filled with mercury. LOTS of weight, very little mass (BIG EPA problem). If you could get it going fast enough it'll melt into an aerodynamic teardrop. HA!

[machintek]

Weight is mass times the force of gravity. Mass is what you use gasoline to accelerate thus giving it kenetic energy which you then must change into heat energy using your brakes and thus the car stops. Using wings and other aerodynamic stuff you can create more downward force measured as weight but actually you are again using energy (gasoline) to create this force. The amount of downward force can be measured also by the increase in drag. Sorry this is so dry!

George
83 911SC Cab/Euro

[Kurt B]

Interesting superman. Well, ultimately you really don't want a lot of mass. I mean, the least mass to a certain point the better.
It's true your weight is merely the mass of your car times the acceleration due to gravity, but every attempt you make to redirect the car or stop it requires greater force applied to components, more energy in the form of friction, and greater stress as the mass increases: tires, rods, gears etc.

Regardless of your down or up force due to aerodynamics and gravity, to brake or turn you're fighting the mass, not the weight, as it would be the same problem if you were racing in a vacuum.

The ideal racing object then would be something like a speeder bike. Very light so not a lot of energy is required to stop or turn it and not as much energy would be required to accelerate it.



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Kurt B
(smashed)1984 Carrera Cabriolet
911 Page
carrera_cabriolet@yahoo.com

[island911]

Kurt are you saying mass in motion will stay in motion unless oppossed by an external force? Can that be right?

"The amount of downward force can be measured also by the increase in drag"

Measured?
The amount of downward force can be CORRELATED to the increase in drag.
Now that's dry!

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'81 Platinum Metalic SC Coupe

[ClayMcguill]

E=MC2

Ol' Al WAS a Genius, it seems.

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Clay McGuill '66 912, '97 Jeep Cherokee www.geocities.com/the912guy

[island911]

If you haven't seen it, check out this '98 GT1 full loop, due to ground effect. . .or lack there of;
http://www.ee.princeton.edu/~wpzclark/carbikestuff/movies/
is on place to get it. The file is named FlyingPorsche.mpg

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'81 Platinum Metalic SC Coupe

[Kurt B]

What I'm really saying is, it's time for Porsche to build a speeder bike. Yo, Stef, let's see if we can't get a speeder bike (a la 'Return of the Jedi' for those under a rock) going by 2004 or so.


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Kurt B
1984 Carrera Cabriolet
911 Page
carrera_cabriolet@yahoo.com

[Bill Wagner]

Since I'm in the mood to beat dead horses tonight, machintek is pretty much right, but weight is actually a measure of force (mass times the gravitational acceleration of the Earth...F=ma). When the statement is made that the F1 and Indy cars need as much weight as possible, they mean that the downforces need to be maximized to keep the car on the road (like machinetek pointed out). Weight is a force, mass is just mass.

Ya know, I probably shouldn't have posted this. It makes me sound like an anal retentive *****!

[Bill Wagner]

WOW! An auto-editing web page. Let's try this instead of the * characters the page assigned me: P-R-I-C-K

There we go!

[lucky77]

Tell it like it is Wagner!

[Bill Verburg]

Weight is the effect of Earths gravity on mass. The relationship F = MA can be reformulated Weight = mass x acceleration due to Earths gravity (W=MG). As long as you stay near the Earths surface the 2 can be used somewhat interchangably.They become very diferent in different gravitational environments. By the way in the Britsh engineering system weight is measured in pounds, mass in slugs, and Earths gravitational acceleration is(1G)is ~32 ft/sec/sec(~32 ft/sec^2). In the MKS system which most of the world uses , mass is measured in Kilograms, force or weight in Newtons, and Earths gravitational acceleration is ~9.8 m/s/s(~9.8 m/s^2)

[ClayMcguill]

If you turned on your headlights (E) while traveling (=) in your Porsche (M) at the speed of light(C2),....would they do anything?

I've always wondered about that.

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Clay McGuill '66 912, '97 Jeep Cherokee www.geocities.com/the912guy

[Early_S_Man]

Actually, Super, you underestimated the weight of F1 and CART cars a bit ... they are in the 1600 lb to 1700 lb area, and in spite of the great advances in engines, suspension, and tires in the mid-'60s, I always was amused by the aerodynamics by the 'cigar rule' featured by the F1 cars in Grand Prix, completely ignoring great advances at the 'other' road racing formula, endurance racing sports cars!

Some things are very hard to improve upon, and the '750 kg' formula of the '30s sounds like the perfect restriction for race cars ... the majority of the USRRC and Can-AM cars of the '60s and '70s would have fit in under that rule ... well, maybe not the 'Honker!'

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Warren Hall
1973 911S Targa

[Kurt B]

Actually clay if that's a serious question then the answer is, they'd shine as normal. The first axiom of relativity is that the speed of light is constant irrespective of one's frame of reference; this is in opposition to everything else in which measured speed is only with respect to a frame of reference--all the cars on the freeway have measured speeds with respect to someone standing still (55 mph), but their speeds with repect to each other are smaller, zero if they're driving side by side.
But light is different. It's always C regardless of how fast you're going when you shine the light. Doesn't matter how fast you're going, it moves the same speed ahead or behind you as it would if you were standing still when you turned it on.


[This message has been edited by Kurt B (edited 06-15-2001).]