A hot air balloon plus its cargo has a mass of 400 kg, and it holds 700 m³ of hot air. It is floating at a constant height in air with a density of 1.29 kg/m³. What is the density of the hot air in the balloon?

Question

Quizplus · Accepted Answer

The buoyant force acting on the balloon equals the weight of the displaced air. Therefore, we have: Buoyant force = Weight of air displaced ρ_air* V_balloon * g = m_balloon * g + m_cargo * g ρ_air = (m_balloon + m_cargo) / V_balloon ρ_air = 400 kg / 700 m³ = 0.57 kg/m³ Therefore, the density of the hot air in the balloon is 0.57 kg/m³. Answer choice B is correct.

A Hot Air Balloon Plus Its Cargo Has a Mass