an iron bar falling through the hollow region of a thick cylindrical shell made of copper experiences a retarding force. what can you conclude about the nature of the iron bar
The iron bar must be a magnet. When the bar magnet falls through the copper shell, it produced change in magnetic flux through it. Due to this, eddy currents are produced in the shell. The eddy currents so produced oppose the fall of the magnet (Lenz's law) and hence bar magnet experiences retarding force