Question

If ${\mu }_k$ is the coefficient of kinetic friction, ${\mu }_r$ is the coefficient of rolling friction and ${\mu }_s$ is the coefficient of static friction, then

• A. ${\mu }_s>{\mu }_k>{\mu }_r$
• B. ${\mu }_s<{\mu }_k<{\mu }_r$
• C. ${\mu }_s<{\mu }_r<{\mu }_k$
• D. ${\mu }_s>{\mu }_r>{\mu }_k$

Answer 1

Answer: (A)

${\mu }_s>{\mu }_k>{\mu }_r$ Rolling friction is always less than sliding friction, that is why it is easy to move a heavy load from one place to another by rolling it over the surface instead of sliding it over the same surface. Moreover, it is quite obvious that static friction is always greater than kinetic friction.