Why does a spinning top not fall?

Have you ever wondered why a spinning top does not fall? It seems like it should be easy for gravity to pull it over, but somehow it stays upright. The answer is that a spinning top has something called angular momentum.

Angular momentum is a measure of how much an object is rotating. It is calculated by multiplying the object's mass by its rotational velocity and the radius of its rotation. For example, a top with a mass of 100 grams spinning at 10 revolutions per second has an angular momentum of 1000 gram-centimeters squared per second.

Angular momentum is conserved, which means that it cannot be created or destroyed. When a top is spinning, it has a lot of angular momentum. This angular momentum resists any changes in the top's rotation. When the top is tilted, the force of gravity tries to pull it over. However, the top's angular momentum resists this force, and the top continues to spin in the same direction.

The faster a top is spinning, the more angular momentum it has, and the more resistant it is to falling over. This is why a top that is spinning very fast is much more stable than a top that is spinning slowly.

Eventually, the top will lose some of its angular momentum due to friction. This friction can come from the air, the surface the top is spinning on, or even the top's own bearings. As the top loses angular momentum, it becomes less stable and eventually falls over.

Here are some additional factors that can affect how long a spinning top will stay upright:

• The shape of the top: A top with a symmetrical shape will be more stable than a top with an asymmetrical shape.
• The weight of the top: A heavier top will be more stable than a lighter top.
• The surface the top is spinning on: A smooth surface will provide more stability than a rough surface.
• The amount of friction: The less friction there is, the more stable the top will be.

So, there you have it! The next time you see a spinning top, you will know why it does not fall. It is all thanks to angular momentum.

We rode bikes on dessert in Las Vegas 2014

Also imagine a person is riding a bike and circling. Her/his front wheel is tint, but still the rider would not fall. The gyroscopic effect that helps to keep a rider upright. But the topic of bicycle balance is more complicated. I would not discuss it here. If you are interested, please go read the paper published in Science in 2011  here.

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