Halliday, Resnick & Walker — Temperature, Heat, and the First Law of Thermodynamics: Problem 24

24 A solid cylinder of radius \(r_1 = 2.5 \text{ cm}\), length \(h_1 = 5.5 \text{ cm}\), emissivity \(0.85\), and temperature \(30^\circ\text{C}\) is suspended in an environment of temperature \(50^\circ\text{C}\). (a) What is the cylinder’s net thermal radiation transfer rate \(P_1\)? (b) If the cylinder is stretched until its radius is \(r_2 = 0.50 \text{ cm}\), its net thermal radiation transfer rate becomes \(P_2\). What is the ratio \(P_2/P_1\)?