The mass of a hot-air balloon and its cargo (not including the air inside) is 250 kg. The air outside is at a temperature of 10°C and a pressure of 1 atm = 105 N/m2 . The volume of the balloon is 400 m3 . Which temperature below of the air in the balloon will allow the balloon to just lift off? (Air density at 10°C is 1.25 kg/m3.)

a. 37°C
c. 99°C
b. 293°C
d. 200°C


B

Physics & Space Science

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