1. The problem statement, all variables and given/known data At an altitude of 315 m above a lake, a hot-air balloon pilot drops a 2.50 kg sandbag. If the bag comes to a stop 4.50 m below the surface of the lake, what force was applied by the water on it? 2. Relevant equations f=ma, d=df-di 3. The attempt at a solution im kinda completely lost about what to do for this question, so i tried just multiplying the mass by gravity. i could also try finding displacement , but i dont know what to do after if i did that.