Question 22 of 30
To rig a threefold purchase what blocks are required
A
One 2 -sheave and one 3 sheave block
B
Two 3 -sheave blocks
C
Two 2- sheave blocks
D
One 2- sheave bock and a single sheave block
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Answer & Explanation
The correct answer is Option B: Two 3 -sheave blocks.
A threefold purchase, which provides a mechanical advantage of 3:1, requires a block with three sheaves attached to the load (moving block) and a block with three sheaves at the fixed point (standing block). Thus, two 3-sheave blocks are needed.