The dominant form of drag experienced by vehicles (bikes, cars, planes, etc.) at operating speeds is called form drag. It increases quadratically with velocity (essentially because the amount of air you run into increases with v and so does the amount of force you must exert on each small volume of air). Thus

Fdrag=CdAv2Fdrag=CdAv2,

where AAA is the cross-sectional area of the vehicle and CdCdC_d is called the coefficient of drag.