system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: F = ma

If you fell out of a plane and hit terminal velocity, why do you still die when a = 0? 

Why can you push a box at a constant velocity?
gpt
You are right -- a  = 0 when you're falling. But it's not the fall that kills you. The acceleration (or, rather, DECELERATION) that occurs when you hit the ground is immense, and provides the force to kill you.

You'll have to explain the second question a little bit better for me to answer.