If you really know physics.. I wonder if angels had wings on their backs, could they really fly?
well, the wing surface does have to be on either side of the body or the flying object would spiral down like a maple leaf. however, angels, as drawn, cold never exist. for one thing, there is no extra musculature for the wings. notice that flying animals have well developed chest and shoulder muscles. angels just have normal human musculature.
body weight would be an issue. most flying animals have hollow bones. pterasaurs had hollow bones but they had fine interior 'webbing' inside the bone, instead of being completely hollow, that added structural integrity without adding too much weight. an excellent design. in order to fly, angels would need some form of hollowed bones. plus, they would have to crap a lot. carrying a lot of waste matter adds weight. that's why birds crap all the time.
the final problem would be balance. angels have bird wings but no tail feathers. the balance would not allow them to fly. animals without tail feathers, like bats and pterosaurs, have wing membranes that extend farther towards the rear of the body, often attached to the legs.
insects don't have tail wing surfaces but, their bodies are balanced for this and insect flight doesn't work exactly the same as other animal flight. insects are much more complicated; very well designed flyers. there was an article in a science magazine, recently, about robot insects that fly like real insects. it really goes in depth about the miracle of insect flight and how it goes contradictory to much of what we assumed about the physics of flight. all very interesting. stuff we truly only recently understood and are still learning about.
science and physics do not have all of the answers, yet. much of what we assume to be fact is really theory. just like much of what we 'know' of the physics of sailing is actually the physics of slow flight applied to water, because water is also a fluid. however, water is a very special fluid with it's own qualities. properties which make things on this planet possible. since sailing is not a relevant thing, except for play, science has not spent the time to truly understand sailing as they have to understand flight.
even much of what is commonly assumed as fact is really myth. if you look on the net you will see lots of people who are 'authorities' on sailing, or even flight, trying to explain how lift is generated...and teaching totally incorrect information. but i digress.
the long and short? no. as depicted, angels could not fly.