Work = force × distance
= 35 N × 200 m
= 7000 J
To answer the specific problem, the balloon contains 480kg
of helium. I am hoping that this answer has satisfied your query and it will be
able to help you, and if you would like, feel free to ask another question.
Answer:
(a) 
(b) P = 0.816 Watt
Explanation:
(a)
The power radiated from a black body is given by Stefan Boltzman Law:

where,
P = Energy Radiated per Second = ?
σ = stefan boltzman constant = 5.67 x 10⁻⁸ W/m².K⁴
T = Absolute Temperature
So the ratio of power at 250 K to the power at 2000 K is given as:

(b)
Now, for 90% radiator blackbody at 2000 K:

<u>P = 0.816 Watt</u>