You seem to have a difficult time getting your point across. Suppose you have a car on a treadmill, all four wheels of the car on the treadmill. The sensors are hooked up however you want.
Now, you step on the gas pedal – what do you think happens?
Read what I was replying to. It’s an example of a car with wheels on rollers where the car can’t move forward, but the rollers can spin.
But, that’s not what the OP is describing. I can’t fault you for misunderstanding, though, since it was poorly-written.
I already wrote that I agree with Chronos’ conclusion.
What’s poorly written about it? I took what was written in an article by Cecil and substituted “plane” for 'car".
Unless you thinks it’s poorly written because I didn’t specify in the OP that I’m talking about the movement of the car in relation to observers on the still ground.
But I don’t see why everyone assumed different in the plane on a treadmill threads. That’s why I started a thread in “Comments in Cecil’s Columns”.
Real NASCAR car on a real treadmill. The treadmill allows the car’s wheels to travel up to 180 mph without the car moving relative to the ground.
Now what was the question?
I think the misunderstanding is actually with you. If you have the wheels spinning such that the speedometer says 60MPH…and the treadmill is going 60 MPH the opposite direction, the car will be completely stationary to an outside observer.
Seriously? I stated twice that I agree with Chronos (and your links aren’t analogous to my question).
No, the misunderstanding is with you. I clarified “relative to the ground” and “(relative to the bystanders on the ground)” .
If the car is stationary to the outside observer, the treadmill is also.
I have some experience with this exact problem. In 1994 we have a vice president that wanted to go racing. I got detailed to build his race car for this little bit of craziness. Anyway this is a race against the clock to try and hit a average target speed. We found a electronic rally computer that would keep a very accurate track of our speed and average speed. I mounted it in the car, and wired it to a handy speed output from the instrument cluster. All that was left was to input a calibration factor and verify the calibration.
So I did the calculations and called a local speedo repair shop and explained what I needed. Come on down they said.
So down I went. The speedo shop had a set of rollers out back, not a dyno but free spinning rollers hooked to a very large easy to read, very accurate mechanical speedo. They told me that they usually didn’t calibrate above about 60mph, but the unit would work up to 100 mph.
now this is a fairly old facility and the rollers were up against a brick wall at one side of the lot. With a rear wheel drive car this would put the car facing the lot. However I was in a FWD car and found it totally disconcerting to step on the gas while staring at a brick wall 10 feet in front of my face. So I had the speedo shop guy “drive” the car while I checked the display.
He floored it, and up through the gears we went. He stabilized the car at 100MPH indicated. and I checked my calibration. It was off by a bit, so he stopped the car and I redid it.
It took two more tries, but we got the calibration dead nuts on.
Anyway we had no straps, no chains, no nothing holding the car on the rollers. Since this was not a dyno, no load was being applied, and therefore there was no need for restraint.
I will note that the car tends to wiggle side to side a bit, due to the smoothness of the steel rollers. Somewhat disconcerting.
Is this a whoosh? Of course the treadmill as a whole is stationary on the ground. That’s the point of having a treadmill, so you can move forward over a surface without having to move forward in space. The treadmill as a whole is stationary. The track on the treadmill moves backward in relation to the ground.
What are you talking about? The treadmill itself will be stationary…the car itself will be stationary, and the wheels of the car will be moving rapidly while the treadmill belt moves rapidly.
If the treadmill belt instantly adjusts for any increase in power to the car, the car is not going ANYWHERE. Period, unless pushed by an external force not in contact with the treadmill. (This is why a plane will take off just fine on a treadmill…the thrust isn’t coming from the wheels, but rather the propeller or jet engine. On a car, however, since the wheels provide the thrust, they won’t be able to propel the car at all.) What’s the issue here?
You have 30 people telling you the same thing and you continue to tell us that WE are the ones who aren’t understanding.
Not a whoosh, I meant he belt itself. I wanted to know what would happen if you stepped on the gas in a car resting on a treadmill and 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.
No, it won’t. I clarified three times now how the belt will behave in my scenario.
Try reading post #28
Ok…what you seem to be trying to describe is an impossibility. You’re saying the belt will only move if the car has actual forward motion? And yet it’s supposed to run the same speed in the opposite direction?
If the belt speeds up to the speed of the car, the car will stop moving forward, which will then (according to your very odd scenario) stop the belt, which will then allow the car to move forward, which will then move the belt, which will then stop the car, which will then stop the belt.
Your scenario will simply result in a massive feedback loop. The only result of which is the belt operating in the way we are all talking about, or both the car and the belt sitting there doing nothing.
Now, because you can’t actually build a system that would respond to this correctly due to delays in electrical relay time, the belt won’t be able to get up to speed fast enough and the car will simply drive off the treadmill. However, I don’t see what that proves. In the ‘perfect system’ you describe, you’d get the feedback loop which would simply make it operate like a normal treadmill or a dyno.
Your ‘clarifications’ make no sense. Let’s get to basics. I’m going to ask one question at a time.
Do you agree that a treadmill is a certain machine that has a track that moves?
I don’t get why it’s so hard to understand the situation Zhing is asking about. The treadmill is set up so that when the car is moving in one direction at a certain speed with respect to ground, the top surface of the treadmill is moving in the other direction at the same speed, also with respect to ground.
If I’m understanding you correctly, the car stays still to an outside observer and if the rollers were a treadmill belt, it would be moving to an outside observer… That’s not the scenario I’ve described multiple times. Try reading posts #14 and #18.
Please, I’ve had enough of this. Yes, the track moves.
Chronos gave me an explanation I’m satisfied with and I believe it’s correct. Maybe you guys can argue with him.
Yes, but that is just a trivial setup.
And yes, in that case, the car would be going twice the speed of the treadmill (well, the wheels would be going twice the speed of the treadmill).
The thing is…this is essentially equivalent to driving on stationary road, just half as fast in forward speed, so I don’t really understand what the point is. It’s not anywhere close to the same question as a plane on a treadmill, so you can understand our confusion.
The question could have simply been worded “What happens when you run a treadmill under a car running at half the speed of the car?” Which is, the car will move forward at the same rate as the treadmill moves backward.
I don’t mean to be insulting. But what you have said is that if the car is not moving, then the belt isn’t either. You don’t seem to accept what other people are saying, so I’m just trying to break it down. Let me quote you:
So the track moves.
Now let’s say someone uses the treadmill for its intended purpose. He is walking forward on the track. The means of locomotion makes no difference. He can be walking, or riding a bicycle, or driving a car. He is moving forward in relation to the track. The track is moving backward in relation to the person on it. To the outside observer the subject is stationary in space and the treadmill track is moving backward.
So getting back to your quote, ‘If the car is stationary to an outside observer,’ the track is moving backward relative to the car.
And this can be seen in Duckster’s link. To you, the outside observer, the little R/C truck is stationary in space. Yet the treadmill track is clearly moving.
There is no point other than me not knowing what would happen. That’s why I asked.
Not when you consider I already replied that Chronos’ post made sense to me more than half way up the thread and I explained multiple times that both the car and belt move at the same speed to an outside observer.
For one to phrase the question that way, one would already know the answer and wouldn’t need to ask it.
Again, I’ve stated multiple times that I have accepted what Chronos said. If you don’t, you can argue with him if he’s up to it.
In my scenario this doesn’t happen! The track and car are still to an outside observer, or are both moving in opposite directions at equal speed relative to an observer. That’s the way the treadmill is set up! How many more times foes this need to be repeated?
See above. See Chronos’ explanation also.