What part of the engine transforms linear movement into rotational force?

The crankshaft is the component of the engine that transforms linear movement into rotational force. This process occurs during the engine's operation when the pistons move up and down within the cylinders. As the pistons rise and fall due to the combustion process, they create linear motion. The crankshaft is connected to the pistons via connecting rods, and as the pistons move, this linear motion is transferred to the crankshaft, causing it to rotate.

This rotational force generated by the crankshaft is essential, as it ultimately drives the vehicle's wheels and powers various engine components. The design of the crankshaft, with its offset pin arrangement, allows for efficient conversion of the piston’s linear action into the rotary motion needed for the vehicle's operation.

Other components listed, such as the piston, flywheel, and rocker arm, each have distinct roles in the engine's function but do not perform this specific transformation of motion. The piston is responsible for creating linear movement but does not convert it to rotation. The flywheel serves to stabilize the engine’s rotational speed and smooth out fluctuations, and the rocker arm transmits movement from the camshaft to the valves, facilitating air and fuel flow in and out of the engine.