1. The problem statement, all variables and given/known data A balloon with an attached basket and a total mass of 1200 kg is hovering at an altitude of 500m. A bag containing 100kg of sand is emptied over the side of the basket. Find the upward acceleration of the balloon after the sand has been poured out. 2. Relevant equations F=ma 3. The attempt at a solution I have no clue how to start this equation or solve it! Please help!!!