volume_mute
Buoyant Force of Displaced Atmospheric Air
publish date: 2026/05/20 22:17:26.361389 UTC
A large balloon has an external physical volume of \(50\text{ ft}^3\). If the weight density of the ambient air at sea level is exactly \(0.08\text{ lb/ft}^3\), what is the total upward buoyant force exerted by the air on the balloon?
Answer = (1)
Correct Answer
(1) 4
Explanation
According to Archimedes' principle, the buoyant force equals the weight of the displaced fluid (air in this case):
\[ F_b = \text{Volume} \times \text{Weight Density of Air} \]
\[ F_b = 50\text{ ft}^3 \times 0.08\text{ lb/ft}^3 = 4\text{ lb} \]
Reference
Basic Physics: A Self-Teaching Guide