You are riding in a hot air balloon. You have not used the burner for some time and the balloon begins to sink. Assuming that no air is allowed to leave or enter the balloon,
A) the average density of the balloon remained constant and the buoyant force on the balloon became less than its weight.
B) the average density of the balloon became greater than the surrounding air and the buoyant force on the balloon remained constant.
C) the average density of the balloon became greater than the surrounding air and the buoyant force on the balloon became less than its weight.
D) the balloon became heavier.

Question

Quizplus · Accepted Answer

As the balloon cools without losing or gaining air, its density increases because the air inside contracts, making it denser than the surrounding air. The buoyant force, which depends on the volume of displaced fluid (in this case, air), remains constant in terms of its calculation basis but becomes insufficient to support the balloon's increased weight due to increased density, causing it to sink.

You Are Riding in a Hot Air Balloon