The commonly used coefficient of friction for moving a metal load on concrete is approximately

• A. 0.50
• B. 0.65
• C. 0.60
• D. 0.45

Answer: (C)

Friction resisting motion is proportional to the normal force, using a kinetic friction coefficient for moving objects. For steel sliding on dry concrete, the common kinetic friction coefficient is about 0.60. This means the sliding resistance is roughly 60% of the load’s weight. So, to keep a metal load moving on a level surface, you’d expect to overcome about 0.60 times the weight in frictional force, assuming clean, dry concrete and proper contact (like wheels or pads). Real-world conditions such as surface roughness, moisture, debris, and how the load is supported will adjust this value, but 0.60 is the typical, widely used estimate in rigging calculations. The other numbers would predict noticeably less or more resistance than is typical for steel on concrete, so 0.60 is the best practical approximation.