1. The problem statement, all variables and given/known data For a birthday gift, you and some friends take a hot-air balloon ride. One friend is late, so the balloon floats a couple of feet off the ground as you wait. Before this person arrives, the combined weight of the basket and people is 1200kg , and the balloon is neutrally buoyant. When the late arrival climbs up into the basket, the balloon begins to accelerate downward at 0.52m/s^2 What was the mass of the last person to climb aboard? 2. Relevant equations F=ma 3. The attempt at a solution Looked through my notes and I am struggling to find any formula without having a known mass. Any help is appreciated, thanks.