Let’s say a fully booked 747 lands after a long range flight and has to stop after landing using no breaks or reverse thrust or the like. How far would it move before air resistance and friction from the surface stops it? What about if it has to land shortly afte take off for a fully booked long range flight? Presume strip is at sea level and its a day with scattered clouds.
I understand that they are different models with different specs, so just use whichever is the current most common.
Surely this depends upon the runway? It’s going to take a lot longer to stop on an ice runway, isn’t it?
And what about landing on a treadmill? 
Are you asking how long it takes if nothing breaks, or how long it will take without using the brakes?
How long it will take using nothing but air resistance and friction.
How long it will take using nothing but air resistance and friction. Think of it as an aeronautical version of simply letting go of the accelerator of your car and not applying break.
brake -not - break
Its a wind resistance applied against the aerodynamics of the 747.
Would be different in Denver vs Miami due to atmospheric pressure.
My first thought, flip answer to the OP’s question was: “Not very much further than the length of the runway.”
I don’t know how you’d really calculate this- I mean, you could probably calculate the momentum and the other physics what-not based on published figures for the plane, but the big unknown would be the amount of friction, air resistance, etc…
There’s no good way that I can think of to guesstimate how fast the airplane would slow down once on the runway. Plus, a lot would depend on just how the pilot landed. I suspect they could probably do some kind of landing that’s a lot rougher on the airframe, but that would probably reduce the speed a lot if they knew they had no reverse thrust or brakes.
OP specified sea level.
The factors of interest are aerodynamic drag, wheel bearing friction, and tire rolling resistance. Aero drag is proportional to the square of speed, and so tapers off to zero as speed approaches zero; by itself, it’s not enough to achieve a complete stop, which means we really need to know the rolling resistance of those tires. (I’ll disregard wheel bearing friction, since they’re likely roller or ball bearing units with neglibly low friction).
References around the internet provide coefficients of rolling resistance for aircraft tires of 0.01-0.02. For a 747-800 that’s maxed out to 900,000 pounds, assuming a value of 0.01 means 9000 pounds of rolling resistance, and a deceleration of just 0.01 G. to go from 50 to 0 using just the rollling resistance of the tires, you’d need nearly four minutes and 8300 feet of runway. Relative to the mass of the plane, aerodynamic drag below 50MPH can probably be safely disregarded without massively affecting the accuracy of that result.
This of course neglects the first part of the decel, from touchdown (~150 MPH?) speed to 50 MPH, which also would use up a lot of runway. I won’t even try to calculate it due to the inclusion of aero drag, but I’d SWAG it at an additional couple of miles. Basically, coasting from touchdown to a dead stop using no brakes or reverse-thrust, on a fully-loaded 747, I expect you’d need somewhere around four miles.
This. However there have been some cases where aircraft have travel quite a bit past the end of the runway while landing but certainly not “miles”.
Edwards AFB has a runway on the Rogers Dry Lake which is about 7 miles long. It’s assumed that anything, including Space Shuttles, could stop there without brakes. It also has a few 4 mile long runways.
Some figures:
Maximum take-off weight of a 747 is 440 tonnes for the 747-8.
Landing speed is 280 km/h or 78 m/s.
So momentum is 34.23M kg m/s.
It also depends on if the control surfaces are used to increase drag.
I think you are forgetting that a 747 at landing does not weigh as much at takeoff.
The answer is going to strongly depend on wind: quite a difference between landing with no wind and into a nice 20-kt headwind.
In real life, if both wheel brakes and reverse thrust were unavailable (how would that happen?), the best action might be to collapse the nose gear when down to, say, 30 kts.
Mass would have a big effect: much better to burn (or dump) most of the fuel.
One of the OP’s suggested cases was for an emergency landing shortly after takeoff; that’s why I used the MTOW figure in my decel estimate.
If the pilots did not switch off the engines after touchdown the airplane would only stop after it ran out of fuel. IOW, idle forward thrust is enough to overcome normal rolling friction and cruise along at 30-ish mph indefinitely. Or, *pace *bump, until the pavement runs out. 
I’m WAGging here, but I’d bet from touchdown with flaps & spoilers / speedbrakes deployed and no forward thrust (as above), but also no reverse thrust or wheel braking it’d take a couple miles to even slow from 150-ish touchdown to 120ish. IOW, for a typical runway that’s about how fast you’d be going when the pavement ran out.
So you need a lake bed like at Edwards to land. Or maybe a nice long empty flat, stretch of highway? Not something that could be done at a regular airport. And if there are no flaps or spoilers, even that is iffy?
How far Did it take for that 2001 plane which leaked fuel and glided to stop?
Fair comment. But can you safely land a fully loaded 747 in an emergency just after takeoff? The 747 that declared an emergency last week leaving the UK for Las Vegas had to circle for several hours to burn fuel before it could land.
So can the landing gear take a MTOW for landing? And what are the risks when the plane is full of fuel during an emergency landing?
Good question. However most aircraft have emergency brake accumulators to actuate the brakes a few times. If they applied the brakes and held them, this could have slowed the aircraft. Antil-lock brakes would have to be off.
Of course thrust reversors wouldn’t have worked and possibly spoilers neither. I don’t remember if flaps and slats deployed on that aircraft. On some aircraft they will free-fall below certain air speeds.
You can, but it can get a little damp under the wings. Technically, not a 747, but I would wager the basic principle applies. I don’t know if the fully-loaded weight of a 747 at takeoff would carry it past the end of the runway (in a normal landing, with brakes & reverse thrust, as opposed to the OP). However, it would suck to market an aircraft that literally could not return to the airport and land if an emergency was declared 30 seconds into the flight.
A pilot can do a lot of things to keep the death count down, not 100% but down & if you don’t need to use the aircraft again real soon, it really ups your chances.
Big birds can sometimes be made to drag the tail area on first touch down & then with the proper application & luck, he can smash the nose down just right to collapse the nose wheel making the landing use a lot less runway …
Understandably, they do not get to practice this very much and also the simulators would be a bit of a guess as there is not a lot of those type landings to get details from.
When the really strange things all gang up together, just hope the guys up front are very good, lucky and can pray real good even while flying the airplane.
Gil Glider
Mri on the Hudson
Sioux City
etc…