A car rounds a flat curve of radius 50 m with a speed of 20 m/s. What minimum coefficient of static friction between the tires and road is needed for the car to not slide?

Core Concept

For circular motion, the centripetal force is provided by friction: f = mv²/r. The maximum static friction is f_max = μ_s × mg. Setting these equal: μ_s × mg = mv²/r, so μ_s = v²/(rg) = (20 m/s)²/(50 m × 9.8 m/s²) = 400/490 = 0.82. This is closest to option D (0.80).