英语时差：跳伞的科学依据2

Why not? She has reached what’s known as “terminal velocity.” This is when the upward push of air resistance–or the friction she experiences as she falls through the air–is enough to exactly counterbalance the force of gravity. When she first jumped out of the plane, this upward push was negligible. At over a hundred miles per hour, it’s pretty strong. She’ll continue downward at a steady velocity, until she opens her chute.