## tnhuy 2 years ago The mass of hot-air balloon and its occupants is 320 kg (excluding the hot air inside the balloon). The air outside the balloon has a pressure of 1.01x10^5 Pa and a density of 1.29 kg/m3. To lift off, the air inside the balloon is heated. The volume of the heated balloon is 650 m3. The pressure of the heated air remains the same as that of the outside air. To what temperature (in K) must the air be heated so that the balloon just lift off? The molecular mass of the air is 29u

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note: for buoyant force to act, the density of the heated air must be lesser than the air outside of it. do you need further help?

2. tnhuy

i need more detail, such as equation, how to calculate, because i'm not good at physic. this is my assignment, i want to get high bonus score in final test. if you can give me completed solution, i will thank you very much.

ah, if it's an assignment, i'll just give you the eqs. $$\Sigma F= F_B- F_G=0$$ since this is the bottom line before it lifts off. $$F_B = \rho V g= (M_human+m_{heatedair})g$$ $$V=\frac{m}{\rho}$$, so you have to get the mass of the air inside the balloon.