Adeep canyon in the ocean floor is called

The question is asking to state the term that is used that refers a deep canyon in the ocean floor, base on my research and further investigation, I would say that the answer would be Trench, I hope you are satisfied with my answer and feel free to ask for more if you have questions 

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 ∞.

  concave means having an outline or surface that curves inward like the interior of a circle or sphere. so the mirror curves inward.