eli5 Does every part of a ball spin at the same speed?

Question

I was holding a rubber band ball in my hand earlier and tossing it up in the air at about eye level. I noticed that I could see the shape of individual rubber bands on the axis of rotation on the outside of the ball but the edges of the ball were blurry. This got me thinking.. is a ball spinning slower near the axis than it is at the outer edge? Is the earth spinning faster at the equator than it is at the poles? If speed is d/t then the math makes sense to a layman like me that the ball would be rotating slower at the center and faster on the edges. Please help.

edit: holy shit. balls are fascinating.

In: 439

Answer 1

It depends on what measurement of speed you are using to describe the motion.

Lets take the earth as an example we are all familiar with.

Remember that you can describe, measure or calculate these things in different ways for different purposes.

* **Angular Velocity**

Pretend you draw a line from the equator through the center of the earth to the opposite side also on the equator (Say from [Bogota, Colombia to Surabaya, Lampung, Indonesia](https://www.geodatos.net/en/antipodes/colombia/bogota))

At the surface both Bogota and Surabaya are spinning. One way this spin can be measured is the angle covered in a certain time. This is called [Angular Velocity](https://en.wikipedia.org/wiki/Angular_velocity) and for earth it is close to 360 degrees in 24 hours or 15 degrees / hour or 1 degree of angle every 4 hours. **Every place on that line between Bogota and Surabaya is spinning at the same angular velocity.** This measurement of spin speed is helpful for some calculations.

* **Surface Speed**

The more common measurement of speed is the one an outside observer would see if they were looking down at the earth as it spun underneath them.

The earth has a circumference (distance around the middle) of around 40,000 km (25,000 miles) and it spins once a day. By this measure of spin speed at the surface, a person on the equator is travelling at 1667 km/hour (1042 miles/hour)

To calculate the surface speed at other locations you can use math.

At the North Pole and the South Pole, the surface speed is 0. At the equator the speed is the fastest you will get (100% of this speed). At any location between these you will be slower than the equator, but faster than the poles.

[Look here for more detail](https://www.thoughtco.com/speed-of-the-earth-1435093)