In a rope of 1/2 inch diameter, the knot must have no bends smaller than how many inches to prevent efficiency loss?

• A. 3 inches
• B. 1 inch
• C. 2 inches
• D. 4 inches

Answer: (C)

The key idea is that knots should not create very sharp bends; keeping bends at a sufficient radius reduces stress concentrations and preserves rope strength. The guideline here is that bends need to be at least four times the rope diameter. For a rope that is 1/2 inch in diameter, four times that is 2 inches. So no bend should be smaller than about 2 inches to prevent efficiency loss.

Sharper bends compress the fibers more and concentrate load at a small contact area, which weakens the rope at the knot. A bend of 3 inches or 4 inches would still work and provide more safety, but the minimum required to avoid efficiency loss is 2 inches. A bend of 1 inch would be too small and would harm performance.