Which component rotates when the load block is raised or lowered?

The running sheave is a crucial component in hoisting systems, particularly in configurations involving block and tackle systems. When the load block is raised or lowered, it is the running sheave that rotates. This is because the hoist chain, which is another component of the lifting mechanism, moves through the running sheave. As the hoist chain is pulled or released to raise or lower the load, the running sheave rotates around its axle, enabling smooth motion of the load block.

In contrast, the side pull refers to the lateral force applied, which does not inherently involve rotation. The hoist chain primarily transmits the lifting force but does not rotate itself. The trolley, typically used for horizontal movement along a beam or track, does not interact with the raising or lowering motion of the load block. Thus, the running sheave's function as the rotating component during the adjustment of the load block makes it the correct answer.