Planes + Conveyer Belts... Where did the question come from?

All right, first off, I’M SORRY for just adding to the whole Planes + Conveyer Belt neverending saga, but where did this question originate?

I asked this in passing in a passing thread related to the subject, so I think *technically *this isn’t asking the same question twice. But I wanted to know where this question came from. The first place I ever saw it posed was on the Dope, and every cite regarding it seems to refer to Cecil and not the famous physics professor who first posed the question to puzzle his engineering student (a fictional character I just invented to represent everyone else except for Dopers).

Maybe no one knows the origin, but maybe you can tell me.

Oh, and as a PS: has this experiment ever been physically demonstrated using, perhaps, a radio controlled ‘toy’ plane and a real conveyer belt?

Actually, you’re pretty close to the truth. I don’t have a cite for it, but one of the earliest ginormothreads on the subject attributed it to a thought problem posed by a teacher; the idea wasn’t to come up with an actual concrete answer to the question, but rather to cause the students to examine the way people interpret questions. So, to that extent, the teacher’s question has succeeded, probably beyond his wildest expectations.

must… not… reopen… issue…


The question is, deliberately or not, vague and self-contradictory. It cannot be answered strictly as stated. It cannot be tested or proven without the question being rewritten. Planes can take off. Brakes work. People and cars running on treadmills don’t go anywhere. Unless you change the basic question, even though each individual specific part of it is logical and answerable, the question as a whole cannot be answered.

Would it have been a better question if the conveyor went at a constant speed (say twice the takeoff speed of the aircraft)?


For the purposes it was originally intended? No, because then it would have a specific, findable answer, which would have defeated the original purpose of the question. Likewise, if the question had been worded along the lines of “the conveyor belt moves backwards fast enough to cancel out all forward movement, no matter how fast that needs to be.”

Like I said earlier, I did not mean to open this argument back up. You are all being very informative by trying to answer me honestly, but as far as the practical experiment goes I take back my PS question. I was really interested in just finding out where the question originated from.

Oh I swear I want this to be over, but curiousity overcomes me :slight_smile: .