One of the first things they will teach you in engineering design is to start by simplifying the model. So if you’re trying to figure out something like the surface area is a fish you assume it’s a cylinder then the math is easy. Same thing with assuming the object is in a vacuum. If you do that you ignore wind resistance and it makes the math easier. You can come back later and take the wind resistance into account.
What’s with the spherical comments in a vacuum?
One of the first things they will teach you in engineering design is to start by simplifying the model. So if you’re trying to figure out something like the surface area is a fish you assume it’s a cylinder then the math is easy. Same thing with assuming the object is in a vacuum. If you do that you ignore wind resistance and it makes the math easier. You can come back later and take the wind resistance into account.