July 30 (Bloomberg) -- Oh, Sir Isaac, what have they done to your immutable laws?

My Audi Q5 is skipping along a back-country lane, rolling with the rolls, curving with the curves, and making it all look easy, blithely unaware that it’s an SUV subverting a number of Newton’s laws of motion.

These 4,000-plus pounds aren’t supposed to move in non- linear lines so convincingly, nor come to sudden stops so pleasingly.

If the English super-scholar had worked for a modern automobile company, he surely would have posited that weight and a high center of gravity have a proportionate and inverse effect on the rate of fun upon winding roads. (There’s a math formula in there somewhere, but I’ve lost my chalk.)

We’ve come a long way since the days of clunky SUVs and constant worries about rollovers. I’m reminded just how far while driving the Q5, Audi’s new entry into the compact SUV market. In many ways, it drives like an extremely capable sedan.

Sport utility vehicles and their crossover brethren rarely excite me. If I’ve got to haul bodies and gear, I lean toward European-style wagons, which hunker closer to the road and are generally lighter and better-performing. In the U.S., they’re about as popular as lederhosen and haggis, so for the time being we’re stuck.

Audi has been busily filling niches and the Q5 is one of the likeliest. While I’m a fan of the $44,000 Audi Q7, at 16.5 feet long and 5,080 pounds, it raises the B-word -- behemoth.

No Welterweight

Small is in the eye of the beholder or the spin of the marketing department: Compared to the Q7, the Q5 is about 18 inches shorter, four inches narrower and almost 900 pounds lighter. Still, it’s hardly a welterweight. It seats five and pricing begins around $38,000 for the basic trim and almost $50,000 for the “prestige” model.

Competitors include stalwarts like the Acura RDX, Lexus RX, Mercedes GLK and BMW X3 -- with starting prices of $35,000 to $40,000.

In truth you won’t find a dangerous, bad-driving auto in that bunch, largely a result of unibody construction (the same type found on passenger cars), better suspensions, and traction and stability controls, which help minimize rollover risk.

For many buyers, choice comes down to styling.

And in that regard, the Q5 hits middling marks. Viewed from the side, it may best be described as khaki -- thoroughly unobjectionable and highly forgettable. Designers didn’t go out on a limb with the silhouette, essentially a shortened Q7. Whereas the Q7 makes an impression simply by dint of its size, the Q5’s form feels lacking.

Sublime Taillights

Jewel-like details do lift it from malaise, including sublime triangular taillights outfitted with LEDs, which cleverly lift with the tailgate so there are no lines marring their geometric shape. The nose is also successful, as Audi’s confident new oversized grill and LED-eyebrow headlights look utterly at home here. You’ll notice the Q5 coming or going, just not when you’re walking past.

Audi interiors are hard to beat. It seems as if the designers truly want passengers to feel at home, rather than imposing austerity measures or their own strict idea of how electronics should be controlled. Utility is prevalent throughout, from the tailgate that opens wide and full, to a seat pass-through for skis and more than 57 cubic feet of rear storage with seats folded.

If you’re looking for optional gizmos that may or may not enhance your life, they certainly abound, from 3-D, traffic- based navigation to a cup holder that heats or cools. (Weird science!)

A4 Foundation

Bringing us back to the drive, the Q5 is built on the same foundation as the A4 sedan and its underpinnings are sophisticated, including electrically controlled shock absorbers and Quattro all-wheel-drive, which sends 60 percent of power to the rear wheels in normal conditions.

It gets a 3.2-liter V-6 with direct injection that’s good for 270 horsepower and 243 pound feet of torque. (One imagines a turbo-charged 4-cylinder may eventually be available and, with luck, a diesel.) The transmission is a competent six-speed automatic and steering is precise and nicely weighted.

My tester was outfitted with Audi Drive Select, an option only available on the prestige trim, which seems a bit nervy of Audi. ADS changes suspension settings and tweaks both engine response and the points at which the transmission shifts. Drivers can select comfort, auto, individual and dynamic, which is code for sport.

Sugar Pill

Sometimes these modes are more a psychological sugar pill than anything else (“We’re faster now, right?”), but in the Q5’s case even spacey passengers will notice that dynamic mode changes the experience.

Zipping along the road, I can’t quite decide if I’m thumbing my nose at science or using it to the best of my ability.

Perhaps, in fact, the Q5 and its ilk deserve a new scientific classification that is less awkward than the crossover designation. If it looks like an SUV but drives as well as a sedan, perhaps we should call it a sudan.

The 2009 Audi Q5 at a Glance

Engine: 3.2-liter V-6 with 270 hp and 243 lb-ft of torque.

Transmission: Six-speed automatic.

Speed: 0 to 60 mph in 6.7 seconds.

Gas mileage per gallon: 18 city; 23 highway.

Price as tested: $53,000.

Best feature: Handles like a sedan, carries like an SUV.

Worst feature: The rather hefty price.

Target buyer: The driver who wants something in-between.

(Jason H. Harper writes about autos for Bloomberg News. The opinions expressed are his own.)

To contact the writer of this column: Jason H. Harper at Jason@JasonHharper.com.

Last Updated: July 30, 2009 00:01 EDT