Final answer:
The clearance between crankshaft and bearings actually increases as an engine wears, contrary to the claim in the question. Flywheels help smooth out engine vibrations due to their high moment of inertia, resisting changes in rotational speed and evening out the energy from piston firings.
Step-by-step explanation:
The statement that as an engine wears, the clearance between its crankshaft and bearings decreases is false. In fact, as an engine operates over time and wears down, the clearance between the crankshaft and the bearings tends to increase. This occurs due to the gradual wearing away of the bearing material, which leads to a larger gap. As for flywheels, these components are critical in reducing engine vibrations. The flywheel has a significant mass and therefore a high moment of inertia, which allows it to store rotational energy. When a piston fires, it imparts a thrust that accelerates the crankshaft. Without a flywheel, this sudden increase in speed would cause vibrations. However, the flywheel's inertia resists changes in rotational speed, thereby smoothing out the pulses of energy from piston firings and resulting in a more even power delivery and less vibration. This is why flywheels are a standard feature in most conventional piston engines.