Radiation from a Surface to the Sky. A plane surface having an area of 1.0 m is insulated on the bottom side and is placed on the ground exposed to the atmosphere at night. The upper surface is exposed to air at 290 K, and the convective heat-transfer coefficient from the air to the plane is 12 W/m - K. The plane radiates to the clear sky. The effective radiation temperature of the sky can be assumed as 80 K. If the plane is a black body, calculate the temperature of the plane at equilibrium.

4-2* Delermine ihe moments of the 225-N foce shown in Fig. P1-2 abvut pıxints A, E, arnd C. 200 me+-200 mm 100 mn 225 N Fig. Pa-2

*9-72. The cylinder CD af the assembly is heated from T, = 30 °C to T, = 180 °C using electrical resistance. At the lower temperature T, the gap between C and the rigid bar is 0.7 mm. Determine the force in rods AB and EF caused by the increase in temperature. Rods AB and EF are made of steel, and cach has a cross-sectional area of 125 mm. CD is made of aluminum and has a cross-sectional area of 375 mm. E = 200 GPa, Ea = 70 GPa, and au = 23(10)/C a7 mm ல் mm 300் m