Mass Moment of Inertia – 2010-ல் CSK வின் வெற்றி ரகசியம்
6 Minutes
Learn mass moment of inertia and rotational physics for students, exploring the Mongoose bat, flywheels, and tightropes. A Tamil science lesson.
- How mass distribution changes inertia using rods and wood blocks
- Why axes and Mongoose bats hit harder than swords and normal bats
- Swivel chair spins with weights, tightrope balance, and flywheels
What this lesson teaches
Mass moment of inertia is the property of an object that resists any change to its rotational motion, depending not only on how heavy the object is but also on how far its mass is spread from the turning point.
How mass distribution works
When an object begins to spin or stop spinning, it resists that change through rotational inertia. If two objects have the same total mass, the one with its mass packed near the outer ends has a higher moment of inertia than one with evenly spread mass. This makes it harder to start spinning, but once in motion, it also resists stopping much more strongly.
Examples of striking tools
- Swords have mass spread evenly along the blade, making them easy to swing but giving lower impact against wood.
- Axes place most of their mass at the far end, creating a higher moment of inertia that strikes with much greater force.
- A Mongoose bat uses a longer handle and shorter blade so weight sits near the tip, delivering heavier hits to the cricket ball.
- A sledgehammer works on the same idea, delivering high impact because its mass is concentrated at the striking head.
Balancing and changing spin speed
- A person spinning on a swivel chair slows down when stretching dumbbells outward, because spreading the mass increases rotational inertia.
- Pulling those weights in toward the chest lowers the moment of inertia, causing the chair to spin faster.
- Tightrope walkers carry a long pole so its wide mass distribution slows any sudden rotation, giving them time to adjust.
- Spreading arms wide while walking along a narrow path helps balance in the exact same way.
Flywheels and fidget spinners
In a four-stroke engine, burning fuel pushes the piston during only one stroke, while the other three strokes must keep moving without power. An engine uses a flywheel, which is thin at the center and thick around the outer rim. Because its mass sits far from the center, the flywheel has a high moment of inertia and keeps rotating steadily through all four strokes. A fidget spinner uses the same design, placing heavy weights at its outer tips so a single push keeps it spinning for a long time.