Question

If ${\mu }_s,{\mu }_k$ and ${\mu }_R$ are the coefficients of limiting, kinetic and rolling frictions between two given surfaces. Arrange them in ascending order:

• A. ${\mu }_R<{\mu }_S<{\mu }_K$
• B. ${\mu }_R<{\mu }_K<{\mu }_S$
• C. ${\mu }_S<{\mu }_K<{\mu }_R$
• D. ${\mu }_K<{\mu }_R<{\mu }_S$

Answer 1

The correct option is B ${\mu }_R<{\mu }_K<{\mu }_S$

The surface irregularities between two surface interlocks with each other which makes it harder (higher frictional resistance) to overcome it initially, but once the interlocking is broken or overcomes, its easier (less frictional resistance) to slide the surfaces.
Rolling friction has very small values.