Who decides on how much x ray energy is safe

Air enters a compressor operating at steady state at 1.05 bar, 300 k, with a volumetric flow rate of 93 m3/min and exits at 12 bar, 400 k. heat transfer occurs at a rate of 15.5 kw from the compressor to its surroundings. assuming the ideal gas model for air neglecting kinetic potential energy effects, determine the power in put in kw.

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

What are similarities and differences between refraction, reflection, diffraction and absorption?