Question

A $20\text{kg}$ block is initially at rest on a rough horizontal surface. A horizontal force of $75\text{N}$ is required to set the block in motion. After it is in motion, a horizontal force of $60\text{N}$ is required to keep the block moving with constant speed. The coefficient of static friction is

• A. $0.30$
• B. $0.44$
• C. $0.52$
• D. $0.38$

Answer 1

The correct option is D $0.38$

Coefficient of static friction ${\mu }_s=\frac{F_1}{R}=\frac{75}{mg}=\frac{75}{20\times 9.8}=0.38$