How is the crust different from the other layers of the earth?
a) it is hotter.
b) it is thinner.
c) it is mostly liquid.
d) it is under pressure.

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)