The flat earth model is the most commonly used one.

@DareToSayIT Yes but it's not just school problems. For example if you want to calculate whether a building or a bridge holds, you make the same assumptions. Or also in construction and manufaction you use the same ones.

@Luke73 Construction does need precise calculation and while dealing with structures, weight/load is what taken into account. Weight of something in Alaska would slightly vary if it’s weighed in Hawaii. It all evens out when you consider the load and not just the mass.

@DareToSayIT That's actually wrong, you assume the gravity of the earth with 9.81 m/s^2. It's standardized.

@Luke73 as I said, its load. Mass x gravity. Force is what considered in construction, not mass. Whether you balance the beams or you build a structure you do resolution of forces. 9.81 is fairly accurate for anything you build on earth, but it’s not a standardized constant for things that needs precise calculations up to 10th decimal point. If you launch spacecraft with that calculation it will never reach the destination.

@DareToSayIT I'm not speaking about space travel. And even there you don't have calculations up to the 10th decimal point precise, there are too many factors that you don't know exactly enough.

And load is not mass times gravity. Gravity is not a unit or anything. Force is mass times acceleration.

@Luke73 You been using the world “gravity” and “acceleration due to gravity” interchangeably. Hence I was speaking to you in your own language. You seem like you have no idea what you are yapping about.