Sandra pushed a wooden block and it slid across the floor. The wooden block gradually slowed down and stopped after moving 10 meters. Why did the block stop moving?

Asuspension of yeast cells is being grown under anaerobic conditions such that glucose is degraded to ethanol and carbon dioxide. if one wishes to follow this process by monitoring the release of 14co2, at which positions in the glucose molecule would the 14c label need to be incorporated?