Originally Posted by ofajen

Simple. It’s just noting the difference between force and power.

Relative wind speed is what determines the force of air drag acting on bike and rider. But to require power (the rate at which you are doing work) that force must act through a distance and the faster it moves (higher velocity) against that force the more power is needed.

Examples:
1) there is a 30 mph wind. If I just stand there on my bike at the appropriate angle, there is some force acting on me, but I don’t move myself and the bike, so I do no work.

2) 15 mph headwind but I ride into it at 15 mph. Same force is acting on me and the bike with the same relative speed but I’m moving at 15 mph against that force. That takes a considerable amount of work. For me it’s probably in the neighborhood of 350 watts because don’t ride low and am not very aero

3) still air and I manage to ride (briefly) at 30 mph. Same force is acting on me and bike but I’m moving 30 mph against that force requiring twice as much power as 2). Might be 700 watts, explaining why it would be only a brief moment.

Does that help?

Otto