Originally Posted by
SlimRider
It's more difficult to accelerate a heavier mass than a lighter mass.
Inertia always resists any change in motion and is mass-dependent. If the headwind is opposing your motion and slowing you down, it becomes necessary for you to oppose the force of the wind. This requires you to "speed up" or accelerate, as you attempt to make forward progress against the wind. This would require a greater expenditure of energy, for a larger mass.
...so, if I'm just maintaining an absolutely constant speed (no momentary acceleration or deceleration) against the wind (and ignoring the small effect of mass on rolling friction for now), how does changing the total mass of the bike+rider+payload affect the net aerodynamic friction that I need to oppose in order to maintain constant speed? For argument's sake, let's suppose that the variable mass for this experiment has no effect on aerodynamic friction, for instance, filling the handlebars with lead shot, and/or inserting slugs of lead into the seat tube. Let's also suppose, in order to maintain absolutely constant speed against the wind, that I've developed a pedalling technique that has constant torque throughout the complete crank rotation. Or, if you prefer, replace my pedalling with an electric motor that supplies constant torque.