Cycling. For a touring bicyclist the dragcoefficient C1ƒ = 1 CArv22 is 1.00, thefrontal area A is 0.463 m^2, and the coefficient ofrolling friction is 0.0045. The rider has mass 50.0 kg, and herbike has mass 12.0 kg. (a) To maintain a speed of 12.0 m/s (about27 mi/h) on a level road, what must the rider’s power output to therear wheel be? (b) For racing, the same rider uses a different bikewith coefficient of rolling friction 0.0030 and mass 9.00 kg. Shealso crouches down, reducing her drag coefficient to 0.88 andreducing her frontal area to 0.366 m^2. What must her power outputto the rear wheel be then to maintain a speed of 12.0 m/s? (c) Forthe situation in part (b), what power output is required tomaintain a speed of 6.0 m/s? Note the great drop in powerrequirement when the speed is only halved. (For more on aerodynamicspeed limitations for a wide variety of human-powered vehicles, see“The Aerodynamics of Human-Powered Land Vehicles,†ScientificAmerican, December 1983.)
