SYN - Physics Education WALTER UNGLAUB What Is the Difference Between First, Second & Third Class Levers?1 What Are Light-Absorbing Substances Called?2 Which One of Copernicus' Theories Was Incorrect?3 Are the Forces on an Object Balanced When the Net Force Is Zero?4 What Two Factors Determine the Atomic Radius of an Element?5 About the Author Walter Unglaub graduated from the Colorado School of Mines with a B.S. in Engineering Physics and a M.S. Applied Physics. ×