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miken123 · 12-03-2005, 01:42 PM

I have the answer. It's a little more complex than a yes / no but here goes.. try to follow me on this:

Thrust is coming from the jets so that TRIES to push the plane forward,
HOWEVER the plane doesn't move forward*YET* because the as the jets move the plane forward and so the wheels start rolling and the conveyer belt matches the wheels speed so the plane goes no where. Right now the wheels contacting the conveyer are NOT slipping (think not losing traction like a car peeling out) meaning the frictional force (i.e. the opposing force the conveyer belt is providing) will be EQUAL to the forward force (engine jet thrust). This is known as non-slip condition (where the coefficient of friction is u-s (static friction)).

Now is where complexities begin: Let's say the plane keeps on getting more and more thrust.
So the plane is thrusted forwards more and more at the jet's level (usually wings)-this causes the wheels to spin faster and faster (and so does the conveyer belt in the opposing direction in order to match the increasing wheel speed). HOWEVER At some point the thrust *MAY* be so great (and this depends on the particular jet engines' power output..) that the frictional force between the plane's wheels (tires) and the conveyer belt will not be able to match the thrust of the jets!!!

At this point (again this is assuming the jet engines can produce this thrust), the plane's tires start to SLIP at the contact point with the conveyer! At this point the friction between conveyer and tires is FIXED (its the normal force multiplied by the friction coefficient mu-k k for kinetic) Since The thrust of the jets is enough to cause this SLIPPING then the conveyer belt, can't hold the plane back anymore!!! WHY? Well to reiterate this paragraph in layman's terms: The tires are slipping so they are in effect being partially dragged over the conveyer belt (again this is what slip means).

DO NOT CONFUSE THIS WITH WHAT HAPPENS WHEN TIRES ON A CAR "SLIP"!!

THE DIFFERENCE: It's that on a car the tires (that are slipping) are what provide the thrust on the car, so if they slip the car in effect no longer gets all the tires thrust
ON A PLANE WITH TIRES SLIPPING: since its tires ARE NOT what provides the plane's thrust, the plane's thrust will still be based off of the engines at the wings or wherever they may be placed.
FINALLY: Since the tires on the Plane ARE what provide the "Opposing thrust" if you will, and since these "providers of opposite thrust" are now SLIPPING, the plane will get a net forward thrust!

Conclusion:
Once the jet engines provide enough forward thrust (force) to overcome the friction between its tires and the conveyer belt, THE PLANE WILL BEGIN TO MOVE FORWARD.

NEW QUESTION!!!!--> Now the plane is moving forward, but will it lift off?
Answer, assuming the jet engines can provide enough thrust --it takes more than it would if there wasn't that opposing force from the slipping wheels -- and that for the sake of this argument, the conveyer belt is long enough so that the plane's forward motion doesn't get to the point where it falls off the conveyer belt's end, YES it will eventually gain enough forward speed to lift off.

NOTE the assumptions of the engines having enough power to:
#1) Generate enough forward thrust to cause the wheels to go into 'slip'
#2) once in 'slip' generate enough added thrust on top of that to reach the lift of speed required.
IF ASSUMPTION 2 IS NOT MET:
The plane will move forward but never fast enough to take off
IF ASSUMPTION 1 IS NOT MET:
The plane won't even move forward

Thank you and have a nice day. If you don't understand the explanation contact a dynamicist or read one of the numerous Dynamics text books, i recommend Craige's Engineering Science and Mechanics: Dynamics.
You may need to read Craige's Statics text first, and possibly read a book in physics before that for a quick background.

12-03-2005, 01:42 PM	#14 (permalink)
miken123 1.4 Liter Trubocharged ECOTEC Join Date: Jan 2003 Posts: 92	Re: Will it take off? I have the answer. It's a little more complex than a yes / no but here goes.. try to follow me on this: Thrust is coming from the jets so that TRIES to push the plane forward, HOWEVER the plane doesn't move forwardYET because the as the jets move the plane forward and so the wheels start rolling and the conveyer belt matches the wheels speed so the plane goes no where. Right now the wheels contacting the conveyer are NOT slipping (think not losing traction like a car peeling out) meaning the frictional force (i.e. the opposing force the conveyer belt is providing) will be EQUAL to the forward force (engine jet thrust). This is known as non-slip condition (where the coefficient of friction is u-s (static friction)). Now is where complexities begin: Let's say the plane keeps on getting more and more thrust. So the plane is thrusted forwards more and more at the jet's level (usually wings)-this causes the wheels to spin faster and faster (and so does the conveyer belt in the opposing direction in order to match the increasing wheel speed). HOWEVER At some point the thrust MAY be so great (and this depends on the particular jet engines' power output..) that the frictional force between the plane's wheels (tires) and the conveyer belt will not be able to match the thrust of the jets!!! At this point (again this is assuming the jet engines can produce this thrust), the plane's tires start to SLIP at the contact point with the conveyer! At this point the friction between conveyer and tires is FIXED (its the normal force multiplied by the friction coefficient mu-k k for kinetic) Since The thrust of the jets is enough to cause this SLIPPING then the conveyer belt, can't hold the plane back anymore!!! WHY? Well to reiterate this paragraph in layman's terms: The tires are slipping so they are in effect being partially dragged over the conveyer belt (again this is what slip means). DO NOT CONFUSE THIS WITH WHAT HAPPENS WHEN TIRES ON A CAR "SLIP"!! THE DIFFERENCE: It's that on a car the tires (that are slipping) are what provide the thrust on the car, so if they slip the car in effect no longer gets all the tires thrust ON A PLANE WITH TIRES SLIPPING: since its tires ARE NOT what provides the plane's thrust, the plane's thrust will still be based off of the engines at the wings or wherever they may be placed. FINALLY: Since the tires on the Plane ARE what provide the "Opposing thrust" if you will, and since these "providers of opposite thrust" are now SLIPPING, the plane will get a net forward thrust! Conclusion: Once the jet engines provide enough forward thrust (force) to overcome the friction between its tires and the conveyer belt, THE PLANE WILL BEGIN TO MOVE FORWARD. NEW QUESTION!!!!--> Now the plane is moving forward, but will it lift off? Answer, assuming the jet engines can provide enough thrust --it takes more than it would if there wasn't that opposing force from the slipping wheels -- and that for the sake of this argument, the conveyer belt is long enough so that the plane's forward motion doesn't get to the point where it falls off the conveyer belt's end, YES it will eventually gain enough forward speed to lift off. NOTE the assumptions of the engines having enough power to: #1) Generate enough forward thrust to cause the wheels to go into 'slip' #2) once in 'slip' generate enough added thrust on top of that to reach the lift of speed required. IF ASSUMPTION 2 IS NOT MET: The plane will move forward but never fast enough to take off IF ASSUMPTION 1 IS NOT MET: The plane won't even move forward Thank you and have a nice day. If you don't understand the explanation contact a dynamicist or read one of the numerous Dynamics text books, i recommend Craige's Engineering Science and Mechanics: Dynamics. You may need to read Craige's Statics text first, and possibly read a book in physics before that for a quick background.