How efficient is an incandescent light bulb?

That depends on what you want to use them for.

As sources of light, they are somewhere around 15% - 20% efficient.

As heaters, they are somewhere around 80% - 85% efficient.

If there was no gravity then their would be no downword force on the football to have it return the the grownd, and if there was no friction (mainly air friction) then there would be no opposing force the stop the ball from moving through the air allowing the ball to travle ∞.