You are using tackle number 2 as shown in illustration D029DG below to lift a weight of 100 lbs. If you include 10 percent of the weight for each sheave for friction, what is the pull on the hauling part required to lift the weight?
• Identify how many parts of the line actually support the moving block/weight in tackle #2 • First find the ideal mechanical advantage (no friction), then adjust for friction by adding 10% of the load per sheave • Remember that each sheave adds friction to the system, effectively increasing the load you must lift
• Looking at tackle #2, how many rope segments are directly sharing the 100 lb load on the moving block? • If there were no friction, what would the pull on the hauling part be, based on that mechanical advantage? • How does adding 10% of the 100 lb weight for each sheave change the effective load that your tackle must lift before you divide by the mechanical advantage?
• Count the exact number of sheaves in tackle #2 (both upper and lower blocks) • Confirm the number of supporting parts of the line attached to the moving block – this sets the ideal mechanical advantage • Compute the adjusted load by adding 10% of 100 lbs for each sheave, then divide by your ideal mechanical advantage before choosing an answer
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