Flywheels used in automobiles and steam engines producing rotational motion have discs with large moment of inertia. Explain why?
Answers
so that the huge transfer of energy toes place
Answer:
A flywheel is basically nothing but a storehouse of energy. It has very high moment of inertia, which is why once it gets into motion, it is almost as though it is in perpetual motion. If you've lived in India, you might have seen the machine a local sugarcane juice vendor uses. He will mechanically rotate a large wheel which has a weight attached to it in a manner that when the wheel is in motion, it becomes practically unstoppable. After that, as he passes the sugarcane through the gears, they literally just pull the tough canes through, wringing out the juice from them. That's nothing but a flywheel in action.
Now, a typical automotive engine will have four strokes, only one of which generates power. All the other three strokes take power away from the crankshaft. So, while in theory, the engine will run because of compression and de-compression, the energy to keep it going is generated only during one cycle, that's the power stroke. What a flywheel does is, it stores this energy, and keeps the engine going through the other strokes by providing the energy back. Diesel engines require more energy through the other strokes owing to higher compression ratios. That's why they have larger flywheels. And hence, diesel engines typically have greater amount of torque as compared to similar sized petrol engines.