Why does a helicopter lift off the ground?

[A.T.]

What I think AT isn't getting about which side is "responsible" is that it isn't the difference between the two that you need to look at to see which is "responsible", but the change in each that you need to look at.

I get what you mean. I just think that your definition of "responsible" is arbitrary. Those discussions about "causes" of lift are bad enough. But this goes a step further and tries to quantify the contribution of opposing forces to the net force on an object.

 

[gianeshwar]

Thank You very much dear friends for an informative discussion!
Through your valuable arguments,my commonsense ideas improved to indepth ones and I got motivation to study and think more.