Your friends have offered to let you use their racing wheels. They each claim theirs is the best. A rider goes up a hill at an 80 cadence. A pursuit rider wants some new wheels. He measures the weight and rotational inertia of several aero wheels and disks.
Air density makes a difference in estimates of performance and it changes from day to day.
A rider is doing a TT and sits up 300m to go. Realizing the mistake, the rider sprints to the end. Afterwards the coach says the time would have been better by 30 seconds if the rider had not sat up. The watts are 293. The rider pedals by pushing down on the pedals only.