Question

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

• A. 0.38
• B. 0.44
• C. 0.52
• D. 0.60

Answer 1

Answer: (A)

0.38

Answer 2

Coefficient of static friction $\mu _ { S } = \frac { F _ { l } } { R } = \frac { 75 } { 20 \times 9.8 } = 0.38$ .