QuoteOriginally posted by: NorthernJohnQuoteOriginally posted by: AaronAccording to a television commercial, a Lexus can go 4,000 feet from a standing start in less time than one dropped the same distance from a helicopter.Unless it is equipped with a jet engine, a car accelerates only by moving the wheels, which provide force only to the extent the tires generate friction with the ground. Unless the wheels are held to the ground in some way, the frictional force cannot be greater than the gravitational force on the car..That is simply not true. You can have a coefficient of friction greater than one even without "sticking". I do not know where this idea comes from that coefficient of friction only has the range 0-1. Why should it?John is right -- the coefficient of static friction usually refers to Coulomb friction as opposed to adhesive ("sticking") friction. Even with simple Coulomb friction a good tire on dry pavement should have a coefficient of static friction of about ~1.7, much less on wet pavement, leading to those old stopping distance diagrams from drivers ed.e.g. stopping distance required at 40 mph assuming mu = 1.7:d = 0.5 * v^2 / (mu * g) = 31.6 feet

Okay, okay, I withdrew the physics criminal charges. I still don't believe the Lexus can do it. Let's see what the company has to say.

QuoteOriginally posted by: AaronOkay, okay, I withdrew the physics criminal charges. I still don't believe the Lexus can do it. Let's see what the company has to say.Okay...S=1/2 a t^2S=4000fta=32ft/sec^2As long as the Lexus travels 4000 ft in a little less than 16 sec, there's no problem. But let me add that I don't think the helmet on the 'professional driver' will do much good if the heli pilot 'jumps' the lights and let's the car go too soon.

QuoteOriginally posted by: NQuoteOriginally posted by: AaronOkay, okay, I withdrew the physics criminal charges. I still don't believe the Lexus can do it. Let's see what the company has to say.Okay...S=1/2 a t^2S=4000fta=32ft/sec^2As long as the Lexus travels 4000 ft in a little less than 16 sec, there's no problem. But let me add that I don't think the helmet on the 'professional driver' will do much good if the heli pilot 'jumps' the lights and let's the car go too soon.FWIIW, when we used to dragrace cars, we used to laugh at junkers with the wrong brackets (times) painted on their windshields saying, "they couldn't do the quarter mile in that heap if you drove it off a cliff." Maybe Lexus heard that and realized that their car appeals to a totally different socioeconomic bracket to the types of people who drive cars off cliffs for yarks.-Lugos

High Friction Materials

QuoteOriginally posted by: WilburHigh Friction MaterialsI think the Lexus has an option to upgrade to Gecko tires.

Lexus responds:QuoteThank you for contacting Lexus Customer Satisfaction. We are dedicated to providing superior service. In circumstances that require our attention, we will assist in the resolution process. The Lexus commercial you viewed was not based on technical details, but rather on marketing. We apologize; we do not have any technical details regarding this commercial. It took ten days rather than the promised one, so perhaps someone actually thought about it. I like the phrase, we should adopt it for marketing materials: "The track record claimed is not based on technical details, but rather on marketing."

QuoteOriginally posted by: AaronThe track record claimed is not based on technical details, but rather on marketing.Actually, Lexus spent $1.6 million dropping cars and recovered the technical details as part of an unrelated project. But their legal department advised them against positioning and representations of the product as one which should be dropped from 4,000 feet.****Note: Use of the Lexus product, automobile, or any marketing insiginia, outside of its intended purpose of being driven at legal speeds on maintained public roads and highways, is prohibited under your automobile purchaser's contract.

I saw this commercial recently and the laws of physics are intact if one is to believe the chronology implicit in the sequence of clips. It appears that the ground-dwelling vehicle is allowed to come up to speed BEFORE it's aerial sibling is released in the the wild blue yonder. Thus, it appears that they are claiming that a standard Lexus (with professional driver on a closed course blah blah blah) can achieve a ground speed greater than the average speed experienced during a 4,000 drop (about 172 mph ignoring air resistance).

In reality of course the nuvo riche driver of a lexus would go get a latte first at fourbucks and whilst the other vehicle (deservedly) plumits to it's demise, manage a fender bender in light drizzle, arriving three hours late. Thus the laws of physics and good taste, while seemingly stretched by lexus, survive intact