Asheet of aluminum (al) foil has a total area of 1.000 ft2 and a mass of 3.716 g. what is the thickness of the foil in millimeters (density of al = 2.699 g/cm3)?

Ahot-air balloon takes off from the ground traveling vertically with a constant upward acceleration of magnitude g/4. after time interval δt, a crew member releases a ballast sandbag from the basket attached to the balloon. how many seconds does it take the sandbag to reach the ground? (express your answer in terms of δt)