The power propelling a bicycle and rider goes mostly into
overcoming wind resistance and lifting mass up hills at
normal bicycle speeds. Bearing and tire friction are small but
can equal wind resistance at very low speeds. The electric
motor torque curve is a function of road slope p, rolling
friction coefficient C
roll
(whose value depends on the road
conditions), and wind speed V
w
, cyclist resistance coefficient
C
r
, and total mass m of the bicycle-cyclist system. Equation
(1) represents the equilibrium and equation (2) keeps the
pretend body pressure drag and skin friction drag into
account.