Question

Which is true for rolling friction $\left({\mu }_r\right)$, static friction $\left({\mu }_s\right)$ and kinetic friction $({\mu }_k$)?

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

Answer 1

Answer: (A)

${\mu }_s>{\mu }_k>{\mu }_r$

Static friction is the force of friction is greater than the applied force. On the other hand If you apply a little more force, the object "breaks free" and slides, although you still need to apply force to keep the object sliding. This is kinetic friction. Thus,${\mu }_s>{\mu }_k$.
The rolling friction is the force just resisting the motion when a body (such as a ball, tire, or wheel) rolls on a surface. It is very small resisting force than the other two friction.
Therefore, ${\mu }_s>{\mu }_k>{\mu }_r$