# Physics/math in car commercial **URL:** \ **Category:** Factual Questions\ **Created:** [January 20, 2007, 2:33pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711 "2007-01-20T14:33:41Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![aktep](https://avatars.discourse-cdn.com/v4/letter/a/f0a364/32.png) [@aktep](https://boards.straightdope.com/u/aktep)\ **Post date:** [January 22, 2007, 3:34pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/21 "2007-01-22T15:34:44Z")
[QUOTE=fiddlesticks] I noticed when I saw this commercial during the football games yesterday (the single commercial that wasn’t the rock-em-sock-em robots commercial) that there was fine print at the bottom of the ad saying something to the effect that the “falling car is simulated”. So, no, they did not. [/QUOTE] It says [“Aerial sequence simulated”](http://208.100.26.199/sdmb/showpost.php?p=8171524&postcount=14) which could plausibly mean that just the shots of the call falling, shown from above, are fake. ---
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [January 22, 2007, 4:06pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/22 "2007-01-22T16:06:52Z")
[QUOTE=Sapo] I think the important thing is that it is plausible. That the time it would take for the car to run that distance at top speed is less than what it would take it to free fall that same distance. [/QUOTE] I scrounged up my spreadsheet. Assuming [this Lexus](http://autos.yahoo.com/lexus_gs_430_sedan-specs/?p=ext) is the vehicle, I’m using a weight of 3748 pounds, an area of 79 square feet (60 by 190 inches), and a drag coefficient of [1.1](http://www.grc.nasa.gov/WWW/K-12/airplane/shaped.html), which is just my best guess. With that, the terminal velocity is about 193 ft/sec (132 mph) and the time to fall 4000 feet is about 24.7 sec. That’s an _average_ speed of 161 ft/sec, or 110 mph. The shape of the curve: ```auto **Time Vel. Height** 0.0 0mph 4000ft 1.0 22mph 3983ft 2.0 42mph 3933ft 3.0 61mph 3855ft 4.0 77mph 3753ft 5.0 90mph 3629ft 6.0 101mph 3487ft 7.0 109mph 3333ft 8.0 115mph 3168ft 9.0 120mph 2995ft 10.0 123mph 2817ft 11.0 126mph 2653ft 12.0 127mph 2448ft 13.0 129mph 2261ft 14.0 130mph 2071ft 15.0 130mph 1881ft 16.0 131mph 1689ft 17.0 131mph 1497ft 18.0 131mph 1305ft 19.0 131mph 1112ft 20.0 132mph 919ft 21.0 132mph 726ft 22.0 132mph 533ft 23.0 132mph 340ft 24.0 132mph 146ft 24.7 132mph 0ft ``` Note terminal velocity is approached rather quickly. (To head off certain objections: this is not to say the vehicle drop was actually _performed_. But examining the underlying plausibility is still worthwhile.) ---
**Author:** ![JeffB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jeffb/32/188_2.png) [@JeffB](https://boards.straightdope.com/u/JeffB)\ **Post date:** [January 22, 2007, 4:18pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/23 "2007-01-22T16:18:26Z")
So this commercial demonstrates that this Lexus can go 110 mph? Not very impressive. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 22, 2007, 7:20pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/24 "2007-01-22T19:20:14Z")
> [@](#): > > So this commercial demonstrates that this Lexus can go 110 mph? Not very impressive. It’s even worse than that, I think. Why did they pick 4000 feet, specifically? They would have gotten more impressive results with a higher drop. And if they could have gotten more impressive results, they would have. Therefore, I think we can actually conclude that this Lexus can _only_ go 110 mph. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [January 22, 2007, 8:08pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/25 "2007-01-22T20:08:01Z")
[QUOTE=robby] You’d need a coefficient of friction between the tires and the road of greater than one. One of those rocket or jet engine cars should be able to do it, though. [/QUOTE] I wonder what the coefficient of friction on airplane wheels is… ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 22, 2007, 9:20pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/26 "2007-01-22T21:20:55Z")
> [@](#): > > I wonder what the coefficient of friction on airplane wheels is… Irrelevant. And that’s all I’ll say, and all anyone should say, on that topic. ---
**Author:** ![DSYoungEsq](https://avatars.discourse-cdn.com/v4/letter/d/c6cbf5/32.png) [@DSYoungEsq](https://boards.straightdope.com/u/DSYoungEsq)\ **Post date:** [January 22, 2007, 9:30pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/27 "2007-01-22T21:30:22Z")
[QUOTE=Chronos] Irrelevant. And that’s all I’ll say, and all anyone should say, on that topic. [/QUOTE] Come now, we know that they built the runway to be able to go backward as fast as … \ 😛 ---
**Author:** ![iamthewalrus\_3](https://avatars.discourse-cdn.com/v4/letter/i/258eb7/32.png) [@iamthewalrus\_3](https://boards.straightdope.com/u/iamthewalrus_3)\ **Post date:** [January 22, 2007, 10:25pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/28 "2007-01-22T22:25:01Z")
[QUOTE=robby] I wonder if a car that can accelerate at greater than _g_ is even possible. I don’t believe that it is. You’d need a coefficient of friction between the tires and the road of greater than one. One of those rocket or jet engine cars should be able to do it, though. [/QUOTE] As has been pointed out, it’s quite possible. Not only is it possible to get a coefficient of friction greater than one, it’s also not necessary. Those really fast cars have serious wings on the top to push them into the ground, which makes the normal force much more than g. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [January 22, 2007, 11:57pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/29 "2007-01-22T23:57:28Z")
what’s the acceleration (in g’s) of a top fuel dragster? anyone? ---
**Author:** ![MrFloppy](https://avatars.discourse-cdn.com/v4/letter/m/43a26b/32.png) [@MrFloppy](https://boards.straightdope.com/u/MrFloppy)\ **Post date:** [January 23, 2007, 12:42am UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/30 "2007-01-23T00:42:25Z")
yabob in post #9 says 3g and points to a wiki article that suggests 5g. According to [this semi-infamous posting](http://listserv.corvettemuseum.com/cgi-bin/wa.exe?A2=ind0311&L=zr1net&D=0&O=D&P=24956), it is closer to 8g. ---
**Author:** ![MrFloppy](https://avatars.discourse-cdn.com/v4/letter/m/43a26b/32.png) [@MrFloppy](https://boards.straightdope.com/u/MrFloppy)\ **Post date:** [January 23, 2007, 12:49am UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/31 "2007-01-23T00:49:27Z")
Upon further review…That link seems to have incorrect info as notes at the bottom of the page indicate. Apparently though, pulling the chutes causes a deceleration of 5gs. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [January 23, 2007, 12:55am UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/32 "2007-01-23T00:55:49Z")
[QUOTE=MrFloppy] yabob in post #9 says 3g and points to a wiki article that suggests 5g. According to [this semi-infamous posting](http://listserv.corvettemuseum.com/cgi-bin/wa.exe?A2=ind0311&L=zr1net&D=0&O=D&P=24956), it is closer to 8g. [/QUOTE] The 3 g was averaged for the entire 1/4 mile run. The wiki article suggests 5 g during the initial part of the run, which I can believe. Here’s a picture of one with a few stats underneath, including “4.5 G’s”: [http://www.toddpaton.com/2004car.htm](http://www.toddpaton.com/2004car.htm) ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [January 23, 2007, 1:11am UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/33 "2007-01-23T01:11:46Z")
And the wiki article figure of 0 to 100 in 0.8 seconds is actually closer to six (5.7). ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [January 23, 2007, 6:30am UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/34 "2007-01-23T06:30:32Z")
[QUOTE=MrFloppy] Upon further review…That link seems to have incorrect info as notes at the bottom of the page indicate. Apparently though, pulling the chutes causes a deceleration of 5gs. [/QUOTE] From the bottom of your link > [@](#): > > I’ve seen the data from a fueler that is a perennial championship > contender and can say that their launch g’s are between 4.5-5 g’s and do > not diminish to less than 2 g’s throughout the run. The highest > g-loading on the driver, however, is not on the launch. It is when they > pull the chutes. They were traveling at 2 g’s forward and then see 5 g’ > s backward so their body sees a 7 g jolt that persists for a few > seconds. This helps to explain why Kenny Bernstein always seems to be > barely able to breath when they interview him after a run… Quite a > few funny car guys have found out the hard way that the belts weren’t > done up tight enough, including Ron Capps who almost went through his > windshield after pulling the chutes on a run. Other racers have had > detached retinas from a harsh parachute opening. > > To go 250 MPH at half track (660 feet) from a standing start you would > need to pull a constant 3.16 g’s. No where near 8 g’s… If you > accelerated at a constant 4 g’s (88 MPH/sec) you would be doing 396 MPH > in 4.5 seconds (at the finish line) which would give a trap speed well > over the 330 MPH region that is currently measured. > > By the way, at the launch of the car, there is no downforce other than > the vehicle weight. Plant all of it on the back tires and have a > coefficient of friction between the tires and the road of 1.0 and it > will accelerate at up to 1.0 g before breaking the tires loose if the > engine power, etc, is there. (It was the belief that you could not have > a coefficient of friction greater than 1.0 that had physicists claiming > that you could not exceed 200 MPH in the quarter mile. How wrong they > were…) By the same corollary, you can figure out the coefficient of > friction of the start line by the amount of g’s you pull… (Top Fuel > slicks and traction enhancer are good for a coefficient of friction of > 4.5-5. The stuff left at the starting line almost pulls your shoes off > you feet when you walk on it…) So yes, you can pull 1G+ at the start line. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [January 23, 2007, 6:34am UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/35 "2007-01-23T06:34:55Z")
> [@](#): > > (It was the belief that you could not have > a coefficient of friction greater than 1.0 that had physicists claiming > that you could not exceed 200 MPH in the quarter mile. How wrong they > were…) Certainly, mu \> 1.0 is uncommon and remarkable, but was it ever actually considered impossible? I’ve a hunch you could even find some pair of ancient materials which would do better than that. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [January 23, 2007, 1:35pm UTC](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711/36 "2007-01-23T13:35:15Z")
I am thinking of a rack and pinion and see no reason why they couldn’t accelerate at any insane rate you could mechanically create. Once you consider that the rubber is actually bonding with the pavement, well, the sky is the limit, I guess. Are there any “real” cars that can put 1g at a traffic light? I think I remember a friend bragging that his Susuki GSX-750R could do just that (and this was a few years ago). [Previous page](https://boards.straightdope.com/t/physics-math-in-car-commercial/388711.md?page=1)