Friction: Practice Problem & Solution

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Friction. Understanding the underlying formula is key to arriving at the correct answer below:

Friction force always opposes relative motion. Limiting static friction \( \text{f}_{\text{s,max}} \) is proportional to normal reaction \( \text{N} \), so \( \text{f}_{\text{s,max}} = \mu_{\text{s}}\text{N} \). Rolling friction is generally much smaller than sliding friction. The coefficient of friction \( \mu \) is a ratio of forces (friction force to normal force), thus it is a dimensionless quantity. Therefore, option (d) is incorrect.