Final answer:
In a four-stroke internal combustion engine, the crankshaft turns 180 degrees during each stroke including the power stroke.
Step-by-step explanation:
The crankshaft turns 180 degrees in one stroke of a four-stroke internal combustion engine. This can be understood by examining how a four-stroke engine operates. There are four strokes in one cycle: intake, compression, power, and exhaust. The crankshaft completes two full 360-degree rotations for every four-stroke cycle. Thus, each stroke consists of half a rotation, or 180 degrees, of the crankshaft. During the power stroke, which is part of one cycle of operation, the fuel-air mixture is ignited, leading to an increase in pressure that pushes the piston down, and in turn, the crankshaft converts this linear motion into rotational motion.