(a) how much helium (density 0.18 kg/m3) is needed to lift a balloon carrying two people, if the total mass of people, basket, and balloon (but not gas) is 280 kg?
(b) repeat for a hot-air balloon whose air density is 10% less than that of the surrounding atmosphere.

(a) 1555.6m^3

(b) 17284m^3

Explanation:

Density of helium=0.18kg/m^3, density of hot-air balloon=0.18-(0.1×0.18)=0.18-0.018=0.162kg/m^3, total mass of people, basket and balloon=280kg

(a) volume = mass/density=280/0.18=1555.6m^3

(b) volume = mass/density = 280/0.162= 1728.4m^3

answer: the exterior temperature of commercial jet planes as they leave the stratosphere and return to the ground increases steadily.

explanation:

the lower most layer of atmosphere is troposphere which extends from 0 to 12 km above the surface of the earth. the temperature initially decreases as distance is increased from the earth's surface. commercial jets fly in lower part of the stratosphere. the stratosphere extends upto 50 km. the temperature in stratosphere starts rising again due to presence of ozone which traps the uv rays.

thus, when the planes leave the stratosphere and return to the ground, the exterior temperature increases steadily.