A sheet of paper falls slower than one that is crumpled into a ball because the flat sheet has a much larger surface area exposed to air. This increases the air resistance (drag) acting against its motion, which slows its fall. The crumpled ball, having a smaller surface area, experiences less air resistance and thus falls faster even though both have the same mass. The greater air resistance on the flat sheet effectively reduces its acceleration and speed as it falls compared to the compact crumpled ball.