A flywheel is a mechanical device that uses the conservation of angular momentum to store rotational energy, which is a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. The flywheel is a component that must be present in a manual car, and it serves to rotate the engine. The flywheel is the first location where the car engine rotates when the car engine is turned on. Apart from turning the engine, the flywheel also has other functions, namely:

• Saving Mechanical Power: The function of the flywheel is to store mechanical energy to balance the engine so that it continues to have good performance. Mechanical power is the energy created when the engine is running. The flywheel works to balance the mechanical power by storing it.

• Connecting Components to the Clutch: In manual cars, the clutch is a very vital component. The clutch is useful for running the engine and the components in it. In this case, the flywheel functions as a place to install the clutch and connect the components contained in the clutch.

• Balancing the Engine Speed: Another function of the flywheel is to balance the engine speed. It also plays a role in inhibiting the supply of mechanical energy and transmitting rotational energy from the piston to the engine parts. With the flywheel, the engine rotation of the car will be more stable.

• Providing Mass for Rotational Inertia: The flywheel provides mass for rotational inertia to keep the cars engine running. Otherwise, the engine will stall when the driver lets their foot off the accelerator. The flywheel is specifically weighted to the cars crankshaft to smooth out the rough feeling caused by even a slight imbalance. It also allows for an electric starter, as the starter motor engages the starter ring on the edge of the flywheel to begin engine rotation.

• Smoothing Out Pulses of Energy: In automobile engines, the flywheel serves to smooth out the pulses of energy provided by the combustion in the cylinders and to provide energy for the compression stroke of the pistons. The larger the rotational inertia of the flywheel, the smaller the changes in speed resulting from the intermittent power supply and demand.

• Energy Storage: Flywheels are often used to provide continuous power output in systems where the energy source is not continuous. For example, a flywheel is used to smooth the fast angular velocity fluctuations of the crankshaft in a reciprocating engine. In this case, a crankshaft flywheel stores energy when torque is exerted on it by a firing piston and then returns that energy to the piston to compress a fresh charge of air and fuel. A flywheel may also be used to supply intermittent pulses of energy at power levels that exceed the abilities of its energy source.

In summary, the flywheel has several functions, including storing mechanical power, connecting components to the clutch, balancing the engine speed, providing mass for rotational inertia, smoothing out pulses of energy, and energy storage.