What is the smallest radius of an unbanked (flat) track around which a bicyclist can travel if her speed is 31 km/h and the coefficient of static friction between the tires and the road is 0.29?

u = 0.30 v = 29km/h = 8.1 m/s Fc = Ff Fc = (mv^2)/r Ff = u(Fn) Fn = mg Ff = u(mg) (mv^2)/r = u(mg) The mass, m, cancels out, leaving: (v^2)/r = u(g) Plugging in what we know, we get: (8.1^2)/r = .3(9.8) 65.6 = 2.93r r = 22.4 m So, the circle must have a radius of at least 22.4 meters.