What is the main function of a flywheel?

• A. To store rotational energy and smooth power delivery by resisting changes in speed.
• B. To convert rotational motion to linear motion.
• C. To increase torque.
• D. To transmit power between shafts.

Answer: (D)

The main idea is that a flywheel provides inertia to smooth out changes in rotational speed. When the engine delivers bursts of torque, the flywheel stores some of that energy and speeds up slightly; when the torque dips, it releases energy and helps keep the shaft turning at a steadier rate. This resistance to speed changes reduces fluctuations and vibration, giving the drivetrain steadier power delivery. The energy stored in a flywheel is E = 1/2 I ω^2, where I is the moment of inertia and ω is the angular speed; a heavier flywheel (larger I) offers more smoothing.

So the flywheel’s job is not to convert motion, not to increase torque, and not to transmit power between shafts. Those functions are handled by other components, while the flywheel’s primary role is to store rotational energy and smooth the power delivered to the rest of the system.