What is the maximum included sling angle in degrees?

What is the maximum included sling angle in degrees?

• A. 45
• B. 90
• C. 60
• D. 120

Answer: (B)

The important idea is how the sling legs share the load. When two legs lift a load symmetrically, the angle between the legs (the included angle) determines how much force each leg must carry. If φ is that angle, the vertical balance is 2T cos(φ/2) = W, where T is the tension in each leg and W is the load. From this, per-leg tension is T = W / (2 cos(φ/2)). As the included angle grows, cos(φ/2) decreases, so each leg must take more of the load. At a 90-degree included angle, each leg carries about 0.707 of the load (since cos 45° ≈ 0.707), which is still within typical sling ratings. Beyond 90 degrees, the required tension climbs more quickly and can exceed the sling’s capacity or create instability, so 90 degrees is the practical maximum.

The important idea is how the sling legs share the load. When two legs lift a load symmetrically, the angle between the legs (the included angle) determines how much force each leg must carry. If φ is that angle, the vertical balance is 2T cos(φ/2) = W, where T is the tension in each leg and W is the load.

From this, per-leg tension is T = W / (2 cos(φ/2)). As the included angle grows, cos(φ/2) decreases, so each leg must take more of the load. At a 90-degree included angle, each leg carries about 0.707 of the load (since cos 45° ≈ 0.707), which is still within typical sling ratings. Beyond 90 degrees, the required tension climbs more quickly and can exceed the sling’s capacity or create instability, so 90 degrees is the practical maximum.