He was pushed. Went over real easy.
http://www.ferrarichat.com/forum/sports/416526-baseball-pitch-accelerate.html#post142555700 For the record - This was asked elsewhere, and the question begs;
Seriously? Wow... Maybe if the plane was driven by its wheels. Last time I checked driving the wheels on a plane is pretty ineffective once the plane gets off the ground. The thrust provided by the engines doesn't much care about what's going on with the wheels, other than overcoming the negligible amount of rolling resistance provided by the wheels on the tarmac. I'm not going to wade through 100+ pages of discussion to see all the theories laid down but if this myth hasn't been busted here by now, the mean level of intelligence on this board is being brought down by a select few...
There's no wind whatsoever. Frontal, backal, sidal, uppal, downal, diagonal, vertical, horizontal wind = 0. via rubber ducky
I don't know about your airport but at ours I see planes take off quite regularly with no wind. What does wind have to do with it? If you don't turn the engine(s) on, nothing will happen, can we agree on that?
Yes seriously. The way I see it is that wheel speed is irrelevant because if there is no lift being produced the plane will not take off.
Wow. This explains why you can't understand how adding stroke changes displacement... Explain how wheel speed is irrelevant. It is, in fact irrelevant but I have a feeling my reason and yours will be different. In your theory wheel speed is absolutely relevant. In fact, you take in to account no other thing. Please explain. No lift? Did I miss something? Is this plane trying to take off in a vacuum? Are the engines not running? Does something suddenly change the second a plane gets a millimeter off the ground? Explain your definition of thrust (with regards to airplane engines). Please stop drinking whatever you're drinking and smoking whatever you're smoking and listen...the moment the thrust of an engine (jet or otherwise) overcomes the rolling resistance of the tires on the tarmac (or conveyor or whatever method you're imagining), the plane will move forward. If you think this takes a lot of thrust, think about the guy in the Guiness Book of Records who pulled a 747. Rolling resistance does not increase exponentially or even linearly so in relative terms, it takes no thrust to overcome rolling resistance, no matter how fast the wheels are turning. What does the other 245,000 pounds of thrust do once the rolling resistance of the tires is overcome? Please answer this question... Oh wait...I only need to go back as far as the top of this page to get an answer...from a guy with 17,000 hours in a real plane... Holy crap...is this for real? Do people really not get this?
New to this topic and must admit at first glance I thought the plane wouldn't fly. Tricky at first sight. Hence the puzzle and the multipage I guess. But honestly, it just takes seconds to get the picture right if you understand how an airplane flies. Obviously it flies whatever the speed of the ground or conveyor beneath, as the pilot said.
hypothetically, if you have a huge wind tunnel for an aircraft, assuming the tunnel is high enough for a take off. And if the wind is strong enough and the aircraft is standing still even without an engine (other parts are good), the aircraft will be aloft like a chopper. i think its basic physics?
The key to this problem is "the relative wind speed over the wings". We know the engine and propeller alone cannot create enough wind over the wings to fly. We know this because every engine run-up prior to take-off shows what happens when the engine revs up but the pilot holds the brakes on. Turns out, the plane vibrates a lot but not enough lifting of the wings is created to leave the ground. A moving conveyor belt under the wheels would have the same effect as holding the brakes during a run-up. That is, the engine would be roaring, there would be lots of vibration, but the plane would not make any forward progress and the relative wind over the wings would not be enough to generate lift. Because it is a no wind day and there would be no forward movement of the plane relative to a fixed spot on the ground, there would be no relative wind for the wings (other than the breeze created by the prop, which we know from the run-up, isn't enough to make the plane fly). Is this question solved now? .
Where did you get this? This grade school level exercise is a "trick question". The conveyor belt can't change the laws of physics regardless what anyone says. The plane flies, every time.
Only a small percentage of people have gotten this right. My original thought was that the plane flies, but that isn't correct. Let's go back to an important part of the question: "The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation." Let's say that the plane accelerates to 10mph ground speed. The conveyer has to turn the opposite direction 10mph right? But, that act of the conveyer moving changes the wheel speed. So the conveyer can never keep up with it; it's in an infinite loop. The only time everything works is at zero mph. If you really think about it, you have to ask yourself, "...the conveyer has to match the speed of the wheels at any given time..." - speed of wheels in relation to what? The answer is the last choice, the question does not provide for an answer. GT
You seem to be missing the point that it is a very special conveyor belt - one that keeps the plane from moving forward or backward from its fixed position (fixed position to every piece of ground in the area other than the conveyor belt's moving surface). The conveyor belt does not make any relative wind for the wings. It is a no wind day. The wings stay stationary to all of the ground outside the boundary of the conveyor belt. The only wind on the wings is from the prop wash of a revved up engine and we know from run-ups that is not enough wind to lift the plane off the ground. It does not matter what speed the conveyor belt is going. It could stay at 0 mph, it could slowly accelerate to 60 mph, even to 200 mph. It does not matter. As long as the wings stay stationary to all the other ground around, there is zero relative wind added by the movement of the wheels on the conveyor belt - regardless of the conveyor belt's speed. .
I don't agree it is an infinite loop for the conveyor belt. The thrust of the plane's engine will want to pull the plane forward. Some sensor on the conveyor belt would sense the first inch of forward motion of the wheels. The conveyor belt would then start to spin to counter-act that inch of forward movement. The speed of the conveyor belt would be proportional to the engine's RPMs or power setting. The more the throttle is set, the faster the conveyor belt would go to keep the plane stationary to the surrounding fixed ground. The conveyor speed would stabilize to a specific mph based on the engine's level of thrust generated at a specific RPM setting. For a small plane like a Cessna 172, the conveyor belt might turn at 60 mph for half throttle, maybe something like 120 mph at full throttle. But the speed would stabilize, so not infinite. Also, if the RPM was reduced, a sensor behind the wheel would detect the first inch of rearward movement of the plane (relative to the surrounding fixed ground) and reduce the turning speed of the conveyor belt accordingly.
What does the speed of the wheels have to do with taking off? If it was a car, which is driven by the wheels then yeah, car isn't going anywhere. But, the airplanes thrust comes from elsewhere unrelated to the wheels. Imagine a plane landing on this same runway but without any wheel braking forces (we'll say reverse thrust is what is slowing it down). Now image that the conveyer is going at some rate of speed, either direction. When the plane touches down, does it instantly speed up or slow down because of the conveyer? No. Ignoring that there is some frictional resistance that will have an effect, the plane will still land just fine as long as it has a hard surface on which to land. GT
Speed of the wheels has nothing to do with the plane taking off. Only the speed of the relative wind over the wings affects take-off. Since the plane in the hypothetical question has 0 mph of relative wind over the wings, it does not take-off.
Which is the correct answer and was given on post #3. How stupid are you people? Oh and here: Image Unavailable, Please Login
As the plane tries to move forward, the conveyor belt moves in the opposite direction and keeps it in a fixed location relative to all of the surrounding ground (NOT RELATIVE to the moving surface of the conveyor belt). It is the same concept as running your car on the dyno while doing an emissions test. Normally when your speedometer says "30 mph" you can put your hand out the car window and feel 30 mph of breeze. But, when your speedo says "30 mph" while your car is on the spinning dyno, you can put your hand out the car window and the air will be still. .
