You are using tackle number 4 as shown in illustration D029DG below to lift a weight. The hauling part of this tackle is bent to the weight hook of tackle number 11. What is the mechanical advantage of this rig?
• Mechanical advantage of a tackle is usually equal to the number of parts of line supporting the moving block (when you haul on the free end) • When two tackles are used together (a compound tackle), the overall mechanical advantage is generally the product of the individual mechanical advantages • You must pay attention to which block is moving and where the hauling part is made fast or bent to be sure which parts actually support the load
• For tackle number 4 by itself, how many segments of rope directly support its moving block that is attached to the weight? • For tackle number 11 by itself, how many segments of rope directly support its moving block? Is the hauling part on the moving or the fixed block? • If the hauling part from tackle 4 is bent to the weight hook of tackle 11, how does that change which tackle is "pulling" the other, and how do you combine their mechanical advantages?
• Carefully count only the rope parts that are actually lifting the moving block in each separate tackle • Confirm whether the hauling end of tackle 4 is acting as the input force for tackle 11, or vice versa • Before choosing an answer, verify that the final mechanical advantage equals (MA of tackle 4) × (MA of tackle 11) for the way they are connected
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