For any given pair of surfaces, the coefficient of friction is maximum in case of limiting friction.
For steel surfaces, the coefficient of friction is μ = 0.8 and between teflon surfaces, μ = 0.04. A steel block of mass 2 kg kept on a steel surface has a limiting frictional force f. What should be the mass of a teflon block kept on a teflon surface to have the limiting frictional force same as f? Take g = 10m/s2.