^^^ edit if I tie that plane to a wall, and fire up it's engines to 500 mph and blow a 200 mph wind at it, <b>it will fly</b>, with absolutely zero forward momentum, just like a kite! haha!
I wonder what we happen if we put friction-less wheels on a bottle rocket and placed it on a conveyor belt and lit that sucker!! Maybe we would have to tie a whole pack of bottlerockets together. haha!
Absolutely - but it's not the egg that's never hitting the ground. It's just that your time is converging on a number prior to the time it does hit the ground. In my example, the egg will hit the ground at 2 seconds, but you're only allowing time to converge to the instant before 2 seconds. You're just not allowing the full process to play out, which is why the egg never hits the ground. There's nothing illogical about it at all.
here's another good one for mythbusters. If we get the nerdy guy on the show to run on a treadmill and place a JATO Rocket in his backpack....would he overcome the force of the treadmill and fly!
maybe we should test that last one a cat first. We would tie a cat to a skateboard (maybe add some wings) and place it on the treadmill, then first up the JATO and run away!
No. Think of it this way: Plane sits at rest, engines powered down on giant conveyor. Conveyor is not turned on. conveyor belt is not moving. Plane is not moving. Everything is at rest. Turn on conveyor. Belt starts to move plane backwards. Plane engines are still not on and plane is completely powered-down, so the conveyor moves plane backwards. The plane is being moved backwards because the weight of the plane is keeping it on the conveyor. Let's call this "backward pull as a result of weight" (or BPAROW). Pilot of plane turns on engines. Engines pull air from front of plane, over/under the wings, and to back of plane, generating forward thrust. Notice - thrust for the plane is not created by the plane's wheels. As we mentioned in step 2, the weight of the plane on the conveyor is still causing the plane to be moved backwards from the conveyor (we're calling it BPAROW). The conveyor will continue to pull the plane backwards as long as there is BPAROW. In fact, the more weight is supported by the conveyor, the more BPAROW will be generated (the opposite is also true - as less weight is supported by the conveyor, BPAROW will decrease). The pilot increases power to the plane engines. The power to the engines must be greater than the BPAROW force in order for the plane to move forward. Now, with a car, this would be very difficult because thrust is generated through the wheels. The conveyor belt would directly negate the thrust that the car's wheels would generate. For a car, if the belt was generating BPAROW of 45 mph, the car would have to send 50 mph of thrust to the wheels just to move forward at 5 mph. But a plane is different because (a) the forward thrust is not generated by the wheels and (b) as the engines pull air over the wings, the wings generate lift, pulling the plane's weight off of the conveyor (and, as we said before, as the plane's weight is removed from the conveyor, the BPAROW decreases). So, since the plane's forward thrust (from the engines) is not being directly negated by the conveyor, the plane will not have nearly as much struggle to overcome the BPAROW as the car does. The pilot will need to increase power to the engines and eventually the plane will move forward. As the plane moves forward, wind hitting over/under the wings will generate lift, which will decrease the plane's weight on the conveyor, which will, in turn, decrease the BPAROW exponentially until there is no BPAROW. At that point the plane still won't take off yet*. The plane engines have negated the BPAROW but will need to generate even more thrust to get enough air over/under the wings to lift the plane into the air. * note: it is theoretically possible that the conveyor is moving its belt at an enormously fast speed. In this case, if the plane's engines are not strong enough to overcome the BPAROW, the plane will not take off. This is a technical possibility. However, since the plane's wheels are not generating thrust, the belt would have to be EXTREMELY fast and the plane's engines would have to be extremely weak. This technicality is not, however, in spirit with the riddle that was originally created. The riddle's concept was based on an misconception that an airplane's forward thrust is generated through its wheels like car (which it isn't) and a conveyor would therefore negate the forward thrust created by the planes wheels (which it wouldn't because a plane does not thrust itself with its wheels).
Nero I'm not gonna say you "don't get it" ('cause I believe you do). But the riddle isn't explained poorly - you're just being too technically demanding. For example, we could say that the riddle doesn't indicate what planet we're on and how much gravity is being generated by the planet (which greatly affects the plane's weight and ability to take off). The riddle didn't mention anything about atmospheric air quality and how difficult/easy it is for a plane to take off given atmospheric gases. The riddle didn't mention air pressure. It didn't mention how many people are in the plane. It didn't mention how much resistance is generated by the plane's wheel bearings. Now, if you want, you can rephrase the riddle to compensate for such things... ... but that wouldn't me much fun, would it?
if I put wheels on my lawn chair, tie some weather balloons to it and place it on a vertical conveyor belt, would I fly or would the conveyor belt negate my lift.
If the conveyor belt were moving at the speed of light would the Millennium Falcon be able to reach warp speeds?
I agree. I believe you "get it" too, but my point is, how else can you word it. It's not about forward momentum (as my kite example shows)...it's about lift. If you negate the lift of the plane, there is no riddle.
I think this is pretty simple. Like others have pointed out, the conveyor belt is irrelevant because the wheels are not the source of propulsion. If those jet engines/propellers are running, the plane will move forward *at the same speed* that it would if there was no conveyor belt. The thrust is coming from the engines, not from the wheels. So there *is* the same amount of forward motion, there *is* the same amount of pressure/lift generated, and the plane will take off ... in fact, it will look no different from a regular take off. If anything, the conveyor belt actually makes it easier for the plane to take off because by spinning in the opposite direction it reduces friction and enables the plane to accelerate faster.
I have to disagree in the fact that people believe that a planes thrust is generated by wheels rather than by an engine. In your example, you stated you turned on the conveyor belt and the plane moved backwards. If that is true (which it is), then you could come up with a theoretical number that would negate a planes forward momentum, regardless of engine size. What is more challenging to me is the "tying the plane to the wall".
Where this all breaks down, though, is here: while the plane is at rest, or in fact moving backwards even, but let's just say 'at rest', the center of gravity of the plane is actually below the surface of the 'ground' (conveyor belt, whatever). In order to break the inertia which keeps the plane's center of gravity directly under the plane (and in fact beneath the ground's surface), you must first still interact with the force of gravity in the form of the wheels' contact with the surface. In order to transfer the plane's center of gravity to a position in front of it, forward momentum is required. What you are doing is assuming the forward momentum happens. But if this 'magic conveyor belt' does what the experiment actually stipulates that it should do, which is negate the wheels' ability to break that initial standing-still inertia, then no forward momentum can occur. The breaking of the inertia is the critical point. This is why efficiency engineers are always looking for ways to improve our methods of reducing friction. Less friction equals less difficulty breaking standstill inertia. In the experiment, when a plane's engines exert force on the mass of the plane, then its center of gravity would start to shift forward, in an upward-curving arc, from beneath to in front. As is stands still, the direction of the energy of the center of gravity is directly straight down. If you use your backwards-moving idea, that actually shifts the center of gravity upwards and behind (there is no such thing as moving 'backwards', just 'moving'. Any movement shifts the center of gravity up and in the direction of the movement). If you charted it, it would look like an inverted arc, or a bowl-shaped curve. So for the sake of the experiment, the conveyor belt would have to be able to accurately detect and counteract any shift in the center of gravity by shifting it backwards with sufficient force to exactly counteract the center of gravity's shift along that arc. If it does so, the plane cannot move, because the only effective momentum is straight down. If its engines manage to transfer the plane's center of gravity from below to in front, then momentum has occurred, and the conveyor has not done what the experiment stipulates. The plane takes off easily, but the experiment fails. That's all academic though. Speaking personally, I doubt that anyone could ever create such a device which could actually do this.
if the conveyor belt isn't flat and has ripples like a wave machine that cause the plane to bounce, would it go forward on each bounce because of lack of contact with the wave belt or would it be knock backwards back the waves...like an incoming tide.
Correction: on plane, the engines enable the plane to break the initial standing-still inertia, not the wheels. Technically 'backwards' (a term I used) doesn't exist. Technically, also, 'behind' and 'upwards' (terms you used) don't exist either. Both are subjective to a point of view. But since an airplane has front, back, sides and can face a certain direction, let's just say that backwards, behind, upwards and forwards can exist in this experiment, shall we? So, your argument is that a common airplane's engines aren't strong enough to overcome the BPAROW?
I'm still not seeing how anyone is explaining how the plane is generating wind in a stand-still position, regardless of forward thrust. Obviously the plane is moving due to thrust, but that power is being negated by the treadmill.
