In a two-leg lift, increasing the angle from vertical affects the tension in each sling how?

• A. It increases
• B. It decreases
• C. It stays the same
• D. It becomes zero

Answer: (A)

When two slings share a load, the vertical support comes from the vertical components of each sling’s tension. For symmetrical legs, the vertical component is T cos theta for each leg, so the total vertical support is 2 T cos theta, which must equal the load W. Solving gives T = W / (2 cos theta). As the angle from vertical increases (theta gets larger), cos theta decreases, so to keep supporting the same weight, the tension T in each sling must increase. This is why increasing the lift angle raises the tension in each sling. Keep in mind that as theta approaches 90 degrees, the required tension grows very large, which is why large lift angles are avoided in practice.