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How would you weigh a plane without using scales?
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(12 votes, avg: 4.33)
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How would you weigh a plane without using scales?
15,537 Views | (12 votes, avg: 4.33)
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Fly the plane onto a huge ship or an aircraft carrier. Paint a mark on the side of the ship to indicate the water level. Then fly the plane off of the ship, and replace it will increasing amounts of known weight. Continue to add weight until the ship sinks to the same water level that you marked on the side. Then you will know the weight of the plane.
Flying the plane onto a ship is a good answer, but the question is flawed. By using a ship thusly, you have created a scale. Any combination of mechnism + alogrithm use to calculate the weight is a defacto scale. The only way not to use a scale is to employ a truely gifted psychic that has not seen the plane and will not visualize the plane before “getting the weight”. In order to avoid any non-physic influences, better not tell the physic not what it is you want “weighed”.
Measure the wings, and find out the lift of the wings (ie, the maximum amount the plane can take off with) (call it x)
put weights on the plane and get it to take off until it can’t any more. It will take several trys, but you should be able to get it so that the plane can take off with ykg of added weights, but if you try with y+1kg it won’t go.
weight of the plane is x - y.
#3 is right. Good thinking !!!
Force = mass x acceleration.
So if you know Force and Acceleration, then mass can be found out.
Hence…
Weight = Mass x Gravitation Const.
Getting the specs of each part employed to build the plane and add their weigh, plus the amount of gas and other fluids and supplies.
Use a sensor to measure the amount of pressure on the wing bottom per square cm. Multiply this with the area of both the wings. Since the Wings cushion the plane, the entire mass of the plane is supported by air pressure on them.
This gives an idea of the running weight of the plane. Correct for ‘g’ for the altitude and you get the weight on ground. Make sure you reduce the fuel weight and people weight later to get the plane weight.
There is obviously a relation between the surface area of the wings (for lift), the takeoff velocity, and the weight of the plane … which the aircraft manufacturers must be using for making their planes. It should be possible to derive the weight knowing the other two variables.
Fly the plane without passenger, get pilot to tell the information of height from the ground (h), speed of plane (v) and consume of fuel (energy). Then use energy balance method:
total energy = potential energy + kinetic energy
fuel = m*(g*h + 0.5*v)
g is gravity and m is the weight of the plane + pilot.
Plane weight = m - (weigth of pilot)
Done!
I think answer # 11 missing some thing
ChNg is not talking about time, what if plane is flying for the last one hour at the same height and at same speed.
We are burning more fuel but flight is at same speed and height?
What do u say Mr. ChNg????????
Even simpler: measure the area of each of the tires touching the ground. Take the pressure of each tire in psi, multiply that by the area (in square inches) of that tire. That will give you the weight each tire is supporting. Sum the weights, and you have the weight of the plane.
Well, here we need to know:
1. Thrust of the engines F (for each type of the airplane this is known).
2. On low speed we can say that the plane accelerates evenly (nearly as perfect as it would in vacuum, as on higher speeds air resistance starts playing the role), mark a line on runway, say, after 500m of the start point.
3. Launch the plane. Note the time it will take the plane to reach the mark.
4. Calculate the acceleration: a = 2s/t^2.
5. Find the mass: F=m/a.
Put it in water and meaure the water displaced?
No 15 is right. Put it into a small reservoir, the water displaced will increase the water level. Measure the area of the water reservoir with the increase in water level, gives you the cubic volume of water displaced. 1cc of water = 1 gram. The plane needs to float though or you get its volume not its weight. So should work for all presurised aircraft.
I would dip it in a pool, measure the amount of water it spills. Then simple:
Weight = mg
some answers require destroying the plane which is stupid and would not get you a job.
This is a real world situation where if you were an engineer designing a system, and all the sudden you need the weight of the plane for some reason (i.e. Cost estimate to move 30 planes overseas), you would have to come up with a simple cost effective solution. (i.e. Call the manufacturer, Google it, etc.)
The best of the above is measure the pressure in the tires. That number would be way off but would be able to closely approximate it. My own answer would be to get a vehicle to “tow” it by chain and measure the force required by the winch to move it. That could be done in 1 day without using specialized equipment. The resulting number could be used in estimations.
Zman is on the right track. F=ma, so push the plane with a given force and measure the resulting acceleration (rate of change in speed). While relatively small, the effect of rolling friction can be estimated by seeing how long it takes the plane to roll to a stop after force is no longer applied.
Simple: Measure the “footprint of the wheels (square inches) in contact with the ground” (assuming they are typical rubber-based tires like automotive ones). Measure the PSI in the tires. Simple math gives you the weight of the plane. [ psst: square inches of tire and pounds PER square inch - 3 tires total, etc. ]
Put the plane on a magical treadmill that will match the planes velocity going in the opposite direction.
let the air plane land on a big ship measure how far the ship sinks down ‘h’ physics says equal mass of water is displaced by the air plane if the surface are of the ship is ‘a’. the mass of the air plane should be
mass of airplane=(density of water)*h*a;
I’d do this.
let mu be the coefficient of rolling friction of the runway. Make a vehicle of known weight pull the plane. Make sure that the wings of the plane are flat(this can be done) straight and not inclined(so that the vertical air pressure becomes negligible). The amount of fuel spent would be the sum of kinetic energy + frictional heat + horizontal air pressure(eps). eps can be either neglected or approximated to some value. Make sure that the tyres of both the aircraft and vehicle are of same material.
E=0.5*(m1+m2)v^2 + mu*(m1+m2)*g*d.
(d=distance traveled)
m1, mu, v are known. Find m2.
To find mu take a known weight w(with the same material mu). Measure the energy reqd to roll it for a distance d along the runway.
E=mu*w*d.
mu=E/(w*d)
Regards,
J1g54w
I believe the weight must be on the aircraft’s specifications manual, wouldn’t it?
So I would read the specifications
It might sound stupid but it might work
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