What measures the radiation given off by earth

Agas contained within a piston-cylinder assembly undergoes three processes in series: process 12: compression with pv= constant from 1 bar and 1 liter to 4 bar. process 23: constant pressure expansion to 1 liter. process 31: constant volume calculate the pressure and volume at each state, and sketch the processes on a p-vdiagram labeled with pressure and volume values at each numbered stat

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.

How is zig zagging a form of acceleration?