When a rope passes through a block, a standard friction of ____ will be used.

• A. 5%
• B. 15%
• C. 10%
• D. 20%

Answer: (C)

Friction in the rope path over a block causes energy loss as the rope slides across the sheave. In practice, the conventional estimate used for a rope passing through a single block is ten percent. This means about one-tenth of the potential tension is lost to friction, so the effective force you can transmit to the load is reduced accordingly. The other percentages aren’t the standard default for a simple single-block path; they might apply to different configurations or less common assumptions. So, using ten percent provides a simple, consistent rule of thumb for estimating how much friction will shave off the rope’s effort in this setup.