During the daylight, you hold a ruler in a distance of 60 cm away from your eyes, and you find
the size of the Moon to be 0.55 cm (try it yourself!). At night, you use a telescope to observe rock
formations and craters on the Moon to estimate the diameter of the Moon to be about 3500 km

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)