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

This is going to be hard to explain to a 5-year old, but remember vinyl records? No? You only know music as a digital media? Damn.

Well, vinyl records are this big flat “plastic” discs that you put on a record player, and as they turn around, a needle moves through the groves on the record and that plays music. But we don’t need that right now.

What do we need? Well, we need to put a record on a record player, put one lego figurine on the outside edge (A), and one near the inside edge (B). A standard record is 30 cm diameter, so A is at 15 cm of the center, and we’ll place B at 5 cm from the center. Our record is going to turn at 33 1/3 rounds per minute. So if we let the record go for an hour, it will have spun around 33.33*60= 1999.8 times, round up to 2000. So both our figurines have made the same amount of revolutions! But have they traveled the same distance? No!

A, on the outer edge, is traveling around a circumference of π x 30 cm diameter, so 94.25 cm. At the same time, B, on the inner edge 5 cm from the center, is going around a circumference of π x 10 cm diameter, so 31.42 cm.

A travelled at a speed of 1.885 km/h, while B travelled at 0.6248 km/h. A went three times as fast as B!

Now how to transpose this to a ball/the earth? Looking at a record, is as if you’re looking down at the earth from one of the poles. A would be standing somewhere on the equator, while B would be somewhere in Canada, a Scandinavian country, or South-Africa.