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Assignment #4 for marking

1. The solar constant at the Earth’s orbital distance (150 Mkm) is 1367 W/m2, and the Earth’s radiation temperature is 255 K (with an albedo of 0.3). NASA’s Solar Probe Plus mission with orbit the Sun with a radius of 7.1 Mkm. What temperature 𝑇 will the surface of a spherical black body attain at that distance from the Sun (if it is small enough and rotates fast enough to maintain a uniform temperature over its surface)?

2. You are standing still in a darkened room. The air is still and the ambient temperature is 50 C. By not moving you can keep your metabolic rate down to 100 W. What is your sweating rate (in L/h)? Now turn on a fan to help evaporate your sweat (which it has to do to cool you). What is your sweating rate now? Do you see the problem?


Make sure that you indicate your answers appropriately, e.g. "The RMS velocity of air at 273K is v_rms = ... ".

Email your homework to
Submit ONE pdf file, named ENPH257_A4_yourfamilyname.pdf by 08:30am Tuesday June 13th.
If you are one of the Lins or Wilsons, append the initial of your given name to the filename.