# If a plane can take off on a conveyer belt, then why not use conveyer belts? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [March 27, 2018, 3:33pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279 "2018-03-27T15:33:10Z")\ **Posts on this page:** 20\ **Page:** 7
**Author:** ![Batano](https://avatars.discourse-cdn.com/v4/letter/b/b487fb/32.png) [@Batano](https://boards.straightdope.com/u/Batano)\ **Post date:** [March 30, 2018, 6:16pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/121 "2018-03-30T18:16:59Z")
A conveyer belt would shorten landing length, though. ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 6:19pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/122 "2018-03-30T18:19:04Z")
Quick question: Can we all agree that if the treadmill speed \> wheel speed the plane will never take off? ---
**Author:** ![AlsoNamedBort](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alsonamedbort/32/3213_2.png) [@AlsoNamedBort](https://boards.straightdope.com/u/AlsoNamedBort)\ **Post date:** [March 30, 2018, 6:22pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/123 "2018-03-30T18:22:23Z")
> [@nate](#): > > Quick question: Can we all agree that if the treadmill speed \> wheel speed the plane will never take off? If there is a hypothetical force keeping the wheel speed (as determined by how fast the wheels are spinning) from never being greater than the treadmill speed, yes, the plane will not move forward. ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [March 30, 2018, 6:27pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/124 "2018-03-30T18:27:31Z")
> [@nate](#): > > Quick question: Can we all agree that if the treadmill speed \> wheel speed the plane will never take off? NO, once again the airplane doesn’t give a flying fuck what it’s wheel speed is, it flies when there is sufficient airflow across the wings to create lift. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [March 30, 2018, 6:31pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/125 "2018-03-30T18:31:55Z")
> [@nate](#): > > Quick question: Can we all agree that if the treadmill speed \> wheel speed the plane will never take off? Yes, because that can only happen when the speed of all involved parts is 0. (Unless you have a really strong headwind, then your ground speed can be 0, your treadmill speed can be 0, your wheel speed can be 0, but you still get lift.) ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 6:37pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/126 "2018-03-30T18:37:15Z")
> [@Morgenstern](#): > > NO, once again the airplane doesn’t give a flying fuck what it’s wheel speed is, it flies when there is sufficient airflow across the wings to create lift. So what is your answer to the question below? > [@nate](#): > > If I had a video camera focused on a wheel of a plane when it is on this treadmill, and in this video this plane is taking off as you guys imagine, what would I see? > > Multiple choice: > > (A) I see the treadmill moving faster than the wheel. > (B) I see the wheel moving faster than the treadmill. ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [March 30, 2018, 6:53pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/127 "2018-03-30T18:53:52Z")
It doesn’t matter if the treadmill is running backwards at the speed of sound. Once the plane applies thrust it moves forward and when the airspeed is sufficient to create lift, the plane flies. PERIOD. That’s it, there is no more. ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 6:55pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/128 "2018-03-30T18:55:23Z")
> [@Morgenstern](#): > > It doesn’t matter if the treadmill is running backwards at the speed of sound. Once the plane applies thrust it moves forward and when the airspeed is sufficient to create lift, the plane flies. PERIOD. That’s it, there is no more. I don’t see your answer to my question. ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [March 30, 2018, 7:02pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/129 "2018-03-30T19:02:04Z")
You plane is on floats now. Does that help you understand this? ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 7:06pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/130 "2018-03-30T19:06:03Z")
> [@Morgenstern](#): > > You plane is on floats now. Does that help you understand this? I still don’t see your answer to my question. ---
**Author:** ![Mithras](https://avatars.discourse-cdn.com/v4/letter/m/f04885/32.png) [@Mithras](https://boards.straightdope.com/u/Mithras)\ **Post date:** [March 30, 2018, 7:07pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/131 "2018-03-30T19:07:48Z")
You’re trying to make the treadmill speed a function of the speed of the wheels. But in the real world, the wheel speed is a function of the ground/treadmill speed. So in your scenario, what do you believe determines the speed of the wheels? ---
**Author:** ![Folly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/folly/32/3219_2.png) [@Folly](https://boards.straightdope.com/u/Folly)\ **Post date:** [March 30, 2018, 7:09pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/132 "2018-03-30T19:09:35Z")
> [@nate](#): > > Quick question: Can we all agree that if the treadmill speed \> wheel speed the plane will never take off? If you’re maintaining the concept of infinite friction between the wheel and treadmill surface, then how could it be possible for (treadmill speed \> wheel speed)? ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [March 30, 2018, 7:16pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/133 "2018-03-30T19:16:05Z")
> [@nate](#): > > I still don’t see your answer to my question. Your question presupposed violating the laws of physics. At that point, we have no way to guess what you’d see. The treadmill would instantaneously speed up to infinity, the wheels would go just a little bit faster, and the plane would take off. ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 7:16pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/134 "2018-03-30T19:16:12Z")
> [@Folly](#): > > If you’re maintaining the concept of infinite friction between the wheel and treadmill surface, then how could it be possible for (treadmill speed \> wheel speed)? While the axle is moving forward or backward relative to ground, the wheel speed increases or decreases, respectively, relative to the treadmill speed. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [March 30, 2018, 7:19pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/135 "2018-03-30T19:19:25Z")
> [@Telemark](#): > > Your question presupposed violating the laws of physics. At that point, we have no way to guess what you’d see. The treadmill would instantaneously speed up to infinity, the wheels would go just a little bit faster, and the plane would take off. Well, except for the part where the whole kit-n-kaboodle gets turned into a black hole. ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 7:22pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/136 "2018-03-30T19:22:45Z")
> [@Mithras](#): > > You’re trying to make the treadmill speed a function of the speed of the wheels. But in the real world, the wheel speed is a function of the ground/treadmill speed. So in your scenario, what do you believe determines the speed of the wheels? In my scenario, the acceleration force of the plane determines the speed of the treadmill through some sort of control system (I gave an analogy of this earlier using sun & planet gears). So the speed of the wheels is ultimately a function of the plane’s thrust. ---
**Author:** ![Folly](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/folly/32/3219_2.png) [@Folly](https://boards.straightdope.com/u/Folly)\ **Post date:** [March 30, 2018, 7:23pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/137 "2018-03-30T19:23:07Z")
> [@nate](#): > > While the axle is moving forward or backward relative to ground, the wheel speed increases or decreases, respectively, relative to the treadmill speed. And what force is causing the axle to move backward relative to the ground? ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 7:26pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/138 "2018-03-30T19:26:56Z")
> [@Telemark](#): > > Your question presupposed violating the laws of physics. At that point, we have no way to guess what you’d see. The treadmill would instantaneously speed up to infinity, the wheels would go just a little bit faster, and the plane would take off. But my question is based on the assumption that the plane takes off (???). I’m asking what would you see watching the video focused on the wheel/treadmill interaction. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [March 30, 2018, 7:29pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/139 "2018-03-30T19:29:06Z")
> [@nate](#): > > But my question is based on the assumption that the plane takes off (???). I’m asking what would you see watching the video focused on the wheel/treadmill interaction. You are asking the question, “what if A+1=A”? The answer is that that is not a valid mathematical formulation. And you keep asking, “well, what if it is, what then?” ---
**Author:** ![nate](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nate/32/13085_2.png) [@nate](https://boards.straightdope.com/u/nate)\ **Post date:** [March 30, 2018, 7:29pm UTC](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279/140 "2018-03-30T19:29:33Z")
> [@Folly](#): > > And what force is causing the axle to move backward relative to the ground? In the simplified, ideal scenario, nothing. In the closer-to-real-world scenario, friction. [Previous page](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279.md?page=6) [Next page](https://boards.straightdope.com/t/if-a-plane-can-take-off-on-a-conveyer-belt-then-why-not-use-conveyer-belts/811279.md?page=8)