what are the units of stress strain and young’s modulus
Young's modulus Young's modulus is the ratio of stress (which has units of pressure) to strain (which is dimensionless), and so Young's modulus has units of pressure. Its SI unit is therefore the pascal (Pa or N/m2 or kg·m−1·s−2). The practical units used are megapascals (MPa or N/mm2) or gigapascals (GPa or kN/mm2).
Richter magnitude scale The Richter magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (adjustments are included to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquake). The original formula is:[27]