1. The problem statement, all variables and given/known data When a box falls in a vacuum, it accelerates at 10m/s^2 and if the mass is 10kg, then it has a net forfeit of 100N. As it falls for 10s, it has a final speed of 100m/s. At the moment of impact, there is a reaction force of 100N acted upon the box by the earth. But since the final speed where net force=0N is 100m/s, then why does the speed drop to 0? Since there is no other force to bring the speed down (decelerate) to 0m/s, so I'm unsure. 2. Relevant equations Net F=ma 3. The attempt at a solution I'm totally not sure what could bring the speed to zero since even if a body has 0 net force, it can have a high speed. And the only way to bring it to zero is if I have a external force to decelerate it to 0 speed first. Thanks for the help!