What is the mechanical advantage of a Luff, Jigger, or Watch Tackle?

What is the mechanical advantage of a Luff, Jigger, or Watch Tackle?

• A. 2:1 MA
• B. 3:1 MA
• C. 4:1 MA
• D. 1:1 MA

Answer: (C)

The key idea is that mechanical advantage equals the number of rope parts that share the load. A luff, jigger, or watch tackle is set up as a four-part purchase, with four rope segments effectively supporting the moving load. That gives a 4:1 mechanical advantage: you must pull four units of rope to raise the load by one unit (ignoring friction). The arrangement usually uses two pulleys on the moving block and two on the fixed block, creating those four supporting strands. So the best answer is four to one.

The key idea is that mechanical advantage equals the number of rope parts that share the load. A luff, jigger, or watch tackle is set up as a four-part purchase, with four rope segments effectively supporting the moving load. That gives a 4:1 mechanical advantage: you must pull four units of rope to raise the load by one unit (ignoring friction). The arrangement usually uses two pulleys on the moving block and two on the fixed block, creating those four supporting strands. So the best answer is four to one.