How to Weigh a Plane Without a Scale
Finding the weight of an object as large and unwieldy as a plane can be a difficult task, and not surprisingly, you may not have access to a scale that could get the job done. Though weighing an airplane requires you to know specific information, like its tire pressure or acceleration and engine thrust, you can do it through the use of physics principles. Even if you do not have to actually weigh an airplane, it is certainly interesting to find out how such a task is accomplished.
Using Newton's Second Law
Calculate the force of the airplane by finding out the thrust of the airplane engines.
Find the acceleration of the airplane by calculating the change in velocity divided by the time interval at which it was taken.
Plug the numbers into Newton's Second Law which states that the force of an object is equal to its mass times its acceleration.
Solve for mass by switching the formula to read: mass equals acceleration divided by force (m = a/F).
Using Tire Pressure and Tire Displacement
Find the tire pressure of each tire using a gauge.
Measure the area of the tire rubber that touches the ground, using the ruler.
Plug in the values of all tires, one by one, by using the Physics formula, pressure equals force divided by surface area (P = F/A). In this instance, the force is equal to the weight an object asserts on the tires.
Solve the equation by rearranging the values to read that force equals the surface area times tire pressure (F = P x A). When you multiply square inches (surface area) by pounds per square inch (tire pressure), the square inches cancel out and you are left with pounds, which is the weight each tire is carrying.
Add together the values of all the tires to get the combined weight of the airplane.
The second section (using tire pressure and surface area) assumes the airplane has flexible tires. If the airplane has rigid tires, then you have to add into the surface area the extra amount of the tire that is helping to carry the weight of the airplane, even if it does not touch the ground.
- airplane image by Clarence Alford from Fotolia.com