this post was submitted on 29 Jun 2024
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[–] [email protected] 19 points 3 months ago (3 children)

what really fucks me up is combining this with relativistic effects

like what if you had a rod 100,000 km long and you started rotating it around one end. does the other end exceed the speed of light? I know the answer has to be no, which means you're going to get all sorts of weird relativistic effects along the rod

[–] [email protected] 18 points 3 months ago* (last edited 3 months ago)

I have heard this thought experiment before. I think the answer is that there is no perfectly rigid rod. The nudge at one end travels down the rod as a pressure wave at the speed of sound of the material, which will be much slower than the speed of light. And in reality, centripetal force would tear apart a rod well before its tips rotate at light speed.

[–] [email protected] 14 points 3 months ago

If you put clocks on different parts of the rod, they'd get out of sync. It's weird.

[–] [email protected] 9 points 3 months ago (1 children)

The force required to accelerate the outer part above light speed exceeds infinity

[–] [email protected] 4 points 3 months ago

give me a lever big enough and i will turn the world

[–] [email protected] 15 points 3 months ago

My dad pointed this out with ceiling fans/helicopter blades when I was a lad and I've never stopped thinking about it, ever

[–] [email protected] 11 points 3 months ago

I remember this bothering me for a while lol

[–] [email protected] 10 points 3 months ago* (last edited 3 months ago)

Idk this makes sense to me actually. Maybe because I am autistic about 33-1/3rpm records bocchi-cry

Edge go faster make bigger circle in same time, yaw.

[–] [email protected] 9 points 3 months ago* (last edited 3 months ago) (1 children)

Is the point that it shouldn’t work that way, but it does?

It feels intuitive to me because this is how gears work. The speed where the teeth mesh must be the same if they are locked, so a gear fitted to another with half the radius will rotate at half the angular rate of the second gear.

[–] [email protected] 12 points 3 months ago

I think the point is that it's difficult to wrap your mind around. It makes sense when you understand it, but it's confusing.

[–] [email protected] 7 points 3 months ago

Fucking circles, how do they work?

[–] [email protected] 7 points 3 months ago* (last edited 3 months ago)

I fell many of us are just ignoring the last panel where Calvin has been traumatized into insomnia by his dad making him learn stuff outside of school which is the funniest part of the comic to me

Also, it's very intuitive to me now, but I remember learning about angular velocity vs tangential speed. It was a mindfuck trying to understand the concepts beyond just the formulas for the first time

[–] [email protected] 6 points 3 months ago

This is why there are many discussions wether something spins faster tha the earth (i.e. a Beyblade with 10 rpm) while it is most often true that the object in question spins more often around its own axis than the earth does, it does not in fact have a higher speed at its edge. However if the object were scaled at tge size of the earth with the same rpm than it would spin faster in all aspects

[–] [email protected] 5 points 3 months ago

Funny how Calvin's dad was sometimes correct, and sometimes he would just spout nonsense when Calvin asked him a basic question. Original Troll Dad.

[–] [email protected] 4 points 3 months ago

Remember folks,

Velocity at the edge = angular velocity * radius

[–] [email protected] 4 points 3 months ago

just-a-theory faster than light outer rotation.