🔍 Key Concepts

• Mechanical advantage of a block and tackle (count the number of parts of line actually supporting the moving block in tackle #12) • Effect of friction in sheaves when the problem says "include 10 percent of the weight for each sheave" • How to get the required pull by dividing the effective load by the mechanical advantage

💭 Think About

• From illustration 12, how many sheaves are there in total, and how many parts of the line are actually holding up the moving block and weight? • If each sheave adds 10% of the 300‑lb weight as extra load, what total "effective" weight must the tackle lift before considering mechanical advantage? • Once you know the effective weight and the mechanical advantage, what simple division gives you the approximate pull on the hauling part, and which choice is closest?

✅ Before You Answer

• Carefully count the total number of sheaves in both blocks in tackle 12 before calculating friction. • Be sure the mechanical advantage equals the number of supporting parts at the moving block (adjust if the hauling part is on the moving block). • After computing the pull, compare your result to all four choices and pick the one that is numerically closest.