# Car on a treadmill **URL:** \ **Category:** Factual Questions\ **Created:** [September 6, 2008, 8:39pm UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384 "2008-09-06T20:39:50Z")\ **Posts on this page:** 15\ **Page:** 5
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [September 7, 2008, 10:49pm UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/81 "2008-09-07T22:49:43Z")
> [@begbert2](#): > > He’s matching the treadmill to the speed of the car-relative-to-observers, not to the wheels-relative-to-ground/treadmill. As I said a little bit ago, to do this practically, you’d have the treadmill rigged to go backwards at half the speed reported by the car’s speedometer. Then I’m still at a loss. Figure the car is idling, the treadmill is idling, everybody’s relaxed. Driver takes his foot off the brake. The car, with an automatic transmission, starts to roll forward. Treadmill operator jumps up, spills his coffee, says “Where do you think _you’re_ going?!”, turn a small rheostat to spin up the treadmill until the apparent advancement of the car has stopped. In the brief delay, the car has sneaked forward about ten feet. Driver looks at his speedometer, which reads 5 mph. This, I assume, is what he would normally see if he let the car roll forward in first gear on a smooth roadway. Treadmill operator looks at his own speedometer. It also says 5 mph. The car’s wheels and the treadmill’s belt might be moving at twice this speed but… who cares? Speedometers are designed to give the human operator useful info, not gauge every component. Driver steps on the brake. Treadmill operator sees the car being carried backward by the treadmill. He turns the rheostat back toward the start position until the car’s relative movement stops. In the brief delay, the car slides back to its starting point, perhaps overshooting a little. If the intended thought experiment is more complicated than this, then I’m afraid I can’t see what the point of it is, except to get into frenzied debate over the definitions of “movement”, “relative” and “speed.” ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [September 7, 2008, 10:53pm UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/82 "2008-09-07T22:53:50Z")
> [@Zhing](#): > > No. If the car is stationary, the wheels can’t be in motion. And they’re not, overall. They may be spinning like mad, but the mass of the tires isn’t observing a net displacement. Rather like how a person can run on a treadmill and, though his feet are a blur, they don’t manage to escape his relatively blur-free torso. Else we’d have footless joggers clogging up our gyms. ---
**Author:** ![pulykamell](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pulykamell/32/3166_2.png) [@pulykamell](https://boards.straightdope.com/u/pulykamell)\ **Post date:** [September 7, 2008, 10:55pm UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/83 "2008-09-07T22:55:39Z")
> [@Johnny\_L.A](#): > > Christ in crotchless panties! I give up. It’s okay. After all this, I’m still not sure I know what the question is. ---
**Author:** ![begbert2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/begbert2/32/3357_2.png) [@begbert2](https://boards.straightdope.com/u/begbert2)\ **Post date:** [September 7, 2008, 11:01pm UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/84 "2008-09-07T23:01:51Z")
> [@Bryan\_Ekers](#): > > Then I’m still at a loss. > > Figure the car is idling, the treadmill is idling, everybody’s relaxed. > > Driver takes his foot off the brake. The car, with an automatic transmission, starts to roll forward. > > Treadmill operator jumps up, spills his coffee, says “Where do you think _you’re_ going?!”, turn a small rheostat to spin up the treadmill until the apparent advancement of the car has stopped. In the brief delay, the car has sneaked forward about ten feet. Here’s where you’re sticking with the _intent_ of the plane scenario, and thus diverging from the OP. In the scenario by the OP the treadmill operator would have to tweak the treadmill until the treadmill’s observed speed (which equals its speedometer speed) equaled the car’s observed speed (which does _not_ equal its speedometer speed because the treadmill counteracts the speedometer somewhat). This would mean, if the speedometer is going 5mph, the operator would say “Hmm, the car is creeping forward at 5; the track is stationary. Better speed up the track.” If he cranked the treadmill up to 5mph, then he’d say “Hmm, the car is stationary now, but the treadmill’s going faster at 5mph. Better slow it down.” And when he sets the treadmill speed to 2.5 mph, he says “There, the car is creeping forward at 2.5mph (5.0 - 2.5), and the track is going backwards at 2.5 mph. All good.” > [@Bryan\_Ekers](#): > > Driver steps on the brake. Treadmill operator sees the car being carried backward by the treadmill. He turns the rheostat back toward the start position until the car’s relative movement stops. In the brief delay, the car slides back to its starting point, perhaps overshooting a little. Actually the treadmill operator says “Hmm, now the car is going backwards at the same speed as the treadmill; they’re supposed to go the same speed but in _opposite_ directions. Better slow the treadmill down.” The point where the forward motion of the car and the backward motion of the treadmill are equal is of course when the treadmill, and thus the car, is stationary. > [@Bryan\_Ekers](#): > > If the intended thought experiment is more complicated than this, then I’m afraid I can’t see what the point of it is, except to get into frenzied debate over the definitions of “movement”, “relative” and “speed.” I wouldn’t say this is a thought experiment so much as "what is treadmill speed X in the equation “X = Car speed - X”. ---
**Author:** ![Zhing](https://avatars.discourse-cdn.com/v4/letter/z/9d8465/32.png) [@Zhing](https://boards.straightdope.com/u/Zhing)\ **Post date:** [September 7, 2008, 11:03pm UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/85 "2008-09-07T23:03:13Z")
> [@Bryan\_Ekers](#): > > And they’re not, overall. They may be spinning like mad, but the mass of the tires isn’t observing a net displacement. Okay, but if the wheels are spinning, an observer on the ground will see the belt on the treadmill moving. In my example, if the treadmill is moving in relation to the observer and the car is still in relation to the observer, the treadmill is not performing as it should, because: > [@](#): > > the treadmill was set up in a way so the car and the belt moved at the same speed but opposite directions to an outside observer ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 7, 2008, 11:52pm UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/86 "2008-09-07T23:52:34Z")
> [@Zhing](#): > > Pot calling the kettle black? What’s that have to do with me calming down? Don’t you need to calm down by the same standards? All of my posts directed at you were in response to yours. I guess **I** need to calm down. > [@](#): > > Oh you poor victim! Why is Zhing picking on me? > [@](#): > > So fucking what? That the OP could have been explained better is irrelevant after all the further clarification given, much of it directly in response to your posts. > [@](#): > > Now that last quote is clear as fucking day. And what do you write next? > [@](#): > > Where the fuck did that come from? Your comprehension inability is still my fault apparently. > [@](#): > > What the fuck! > [@](#): > > Where the fuck did I say that? How many times at this point did I explain the opposite? A lot! [Moderating] **Zhing** , even if you feel you have been provoked, these kinds of posts are inappropriate for GQ. I think you do need to calm down, and not let your responses get so personal. Take it down several notches, please, or you may receive an official warning. Colibri General Questions Moderator ---
**Author:** ![Zhing](https://avatars.discourse-cdn.com/v4/letter/z/9d8465/32.png) [@Zhing](https://boards.straightdope.com/u/Zhing)\ **Post date:** [September 8, 2008, 1:16am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/87 "2008-09-08T01:16:48Z")
> [@Colibri](#): > > [Moderating] > > **Zhing** , even if you feel you have been provoked, these kinds of posts are inappropriate for GQ. I think you do need to calm down, and not let your responses get so personal. Take it down several notches, please, or you may receive an official warning. > > Colibri > General Questions Moderator That’s fine, but why is this just directed towards me when Johnny L.A. made similar posts? : > [@](#): > > Oh, you poor victim! ‘It isn’t my fault! Nobody understands me!’ > [@](#): > > Well, the time you put into it indicates a certain obsessiveness. > [@](#): > > Excuse me, but do you really blame anyone for being incredulous when someone, in effect, asks ‘What’s thirty plus thirty?’? > [@](#): > > You know, they make decaffeinated coffees that taste just as good as regular coffee. > [@](#): > > It’s like the stereotypical Ugly American who thinks he can make himself understood in a foreign country by talking louder. > [@](#): > > [http://www.youtube.com/watch?v=AShBoF1FPSE](http://www.youtube.com/watch?v=AShBoF1FPSE) ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [September 8, 2008, 1:24am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/88 "2008-09-08T01:24:15Z")
> [@Zhing](#): > > That’s fine, but why is this just directed towards me when Johnny L.A. made similar posts? : I don’t see the word “fuck” in any of those posts. ---
**Author:** ![Zhing](https://avatars.discourse-cdn.com/v4/letter/z/9d8465/32.png) [@Zhing](https://boards.straightdope.com/u/Zhing)\ **Post date:** [September 8, 2008, 1:36am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/89 "2008-09-08T01:36:08Z")
> [@Q.E.D](#): > > I don’t see the word “fuck” in any of those posts. Yes, that is a difference, but is it a relevant one? I see that language used here all the time and Colibri didn’t make it evident that the use of “fuck” was the problem. I’m guessing the warning follows a theme I’m noticing here which is “It’s all the newb’s fault”. I’d bet anything that if the question were asked by Rick or Johnny L.A. (as imperfectly as it was in the OP) and I were to make the same comments Rick and Johnny did, I would have had more than a few posts asking me what my problem is. Just a feeling. I’m betting a few reading this have the same one. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 8, 2008, 1:54am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/90 "2008-09-08T01:54:17Z")
> [@Zhing](#): > > Yes, that is a difference, but is it a relevant one? I see that language used here all the time and Colibri didn’t make it evident that the use of “fuck” was the problem. > > I’m guessing the warning follows a theme I’m noticing here which is “It’s all the newb’s fault”. > > I’d bet anything that if the question were asked by Rick or Johnny L.A. (as imperfectly as it was in the OP) and I were to make the same comments Rick and Johnny did, I would have had more than a few posts asking me what my problem is. Just a feeling. I’m betting a few reading this have the same one. Absolute bullshit. **Rick** and **Johnny L.A.** may have been somewhat snarky, but you were the one who first became seriously obnoxious, in post #44. [QUOTE=Zhing] What the fuck! I didn’t know the answer to what would happen SO I ASKED! That WAS the fucking problem! It finally sunk in what I was asking after I clarified at least five times and now you’re going to act like a genius by giving the answer AFTER SOMEONE ALREADY GAVE IT and I acknowledged that I was satisfied with the answer? Well goody for you! [/QUOTE] Actually, I tend to cut newbies some slack, since they are not aware of standards here. If any oldtimer here had made a post like #44, I would have issued them an Official Warning right off the bat, since they are expected to know what is acceptable. I think this thread has become sufficiently sidetracked, mainly by your efforts, that it might as well be closed. If you have additional questions or want further clarifications about the subject, you may open another thread, as long as you remain polite. If you wish to question my moderating, you may do so in ATMB or the BBQ Pit, as you prefer. Colibri General Questions Moderator ---
**Author:** ![Zhing](https://avatars.discourse-cdn.com/v4/letter/z/9d8465/32.png) [@Zhing](https://boards.straightdope.com/u/Zhing)\ **Post date:** [September 8, 2008, 2:12am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/91 "2008-09-08T02:12:05Z")
> [@Colibri](#): > > Absolute bullshit. **Rick** and **Johnny L.A.** may have been somewhat snarky, but you were the one who first became seriously obnoxious, in post #44. That’s not what you gave me an unofficial warning for. You gave it to me for making the same kind of comments Johnny L.A. did, and mine were in response to his (since who did something first seems to be of some relevance to you). You’re saying it’s bullshit that there would have been more than a few posts asking me what my problem is if I posted what Rick or Johnny L.A. did? I seriously doubt that’s bullshit. Or it’s just bullshit that my warning has nothing to do with my newbness? Then why Is this okay: "Oh, you poor victim! ‘It isn’t my fault! Nobody understands me!’ " But not this: "Oh you poor victim! Why is Zhing picking on me? " What is so wrong with this: “Pot calling the kettle black? What’s that have to do with me calming down? Don’t you need to calm down by the same standards? All of my posts directed at you were in response to yours. I guess I need to calm down.” The post that provoked that response was somehow okay? ---
**Author:** ![Idle\_Thoughts](https://avatars.discourse-cdn.com/v4/letter/i/838e76/32.png) [@Idle\_Thoughts](https://boards.straightdope.com/u/Idle_Thoughts)\ **Post date:** [September 8, 2008, 2:16am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/92 "2008-09-08T02:16:50Z")
> [@Zhing](#): > > \ > > The post that provoked that response was somehow okay? [hijack]Just so you don’t start getting warnings or something worse, allow me to let you know there is a forum for any problems you may have with a mod (or even member’s) opinions or doings: [http://boardstest.straightdope.com/sdmb/forumdisplay.php?f=5](http://boardstest.straightdope.com/sdmb/forumdisplay.php?f=5) I would encourage/strongly suggest that if you had a problem with a member or something against someone else that you would take it here, however please note I am not a mod or admin, just someone who hopes to help out a new person and hopefully give them some sound advice. [/hijack] Sorry with this off topic post. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [September 8, 2008, 2:19am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/93 "2008-09-08T02:19:16Z")
> [@Zhing](#): > > That’s not what you gave me an unofficial warning for. You gave it to me for making the same kind of comments Johnny L.A. did, and mine were in response to his (since who did something first seems to be of some relevance to you). > > You’re saying it’s bullshit that there would have been more than a few posts asking me what my problem is if I posted what Rick or Johnny L.A. did? I seriously doubt that’s bullshit. > > Or it’s just bullshit that my warning has nothing to do with my newbness? Then why Is this okay: > "Oh, you poor victim! ‘It isn’t my fault! Nobody understands me!’ " > > But not this: > "Oh you poor victim! Why is Zhing picking on me? " > > What is so wrong with this: > “Pot calling the kettle black? What’s that have to do with me calming down? Don’t you need to calm down by the same standards? All of my posts directed at you were in response to yours. I guess I need to calm down.” > > The post that provoked that response was somehow okay? **Moderator Warning** I instructed you to take complaints about my moderating to ATMB or the Pit. Do not continue to dispute it here, or your continued posting privileges will be under discussion by the administration. Colibri General Questions Moderator ---
**Author:** ![Zhing](https://avatars.discourse-cdn.com/v4/letter/z/9d8465/32.png) [@Zhing](https://boards.straightdope.com/u/Zhing)\ **Post date:** [September 8, 2008, 2:21am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/94 "2008-09-08T02:21:11Z")
Thanks for the info, Idle Thoughts. I better let it go for my own good. I’m sure this isn’t constructive in any way and I’m just giving myself anxiety for nothing. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [September 8, 2008, 2:35am UTC](https://boards.straightdope.com/t/car-on-a-treadmill/462384/95 "2008-09-08T02:35:14Z")
Closed. **samclem** Moderator GQ [Previous page](https://boards.straightdope.com/t/car-on-a-treadmill/462384.md?page=4)