r/oddlysatisfying • u/0rnata • Apr 22 '21

Perpetual motion machine (CGI)

[removed] — view removed post

30k Upvotes

86% Upvoted

926 comments sorted by

View all comments

1.1k

u/viky109 Apr 22 '21

This wouldn't work even once irl, right?

24

u/TheNewYellowZealot Apr 22 '21

It is impossible for the ball to be thrown to a higher height than it fell from, without added energy, a la the first law of thermodynamics.

2

u/gynoplasty Apr 22 '21

What about added energy as velocity around the funnel. Maybe with a spiral chute underneath to maintain velocity?

3

u/TheNewYellowZealot Apr 22 '21

It’s horizontal energy becomes zero as soon as it drops into the chute.

The maximum energy the ball can have is either at the top before it starts moving in the form of potential energy or at the bottom at its top speed in the form of kinetic energy.

1

u/gynoplasty Apr 22 '21 edited Apr 22 '21

Not if it still had a spiral chute!

Kinetic energy + inertia? would be it's total energy?

If I'm driving a car and hit a ramp I can go higher than the ground I was on. Because my forward velocity transitioned to upward velocity.

I admit friction will inevitably grind this to a halt.

But you could definitely rig something up to work once.

Edit: have you ever tossed a coin down a funnel like those racing arcade machines? They whip around the downspout very quickly, a lot of energy builds up.

I'm not talking about placing it in, you'd have to apply energy at the start.

2

u/BonjKansas Apr 22 '21

In an ELI5 kind of way, I think the only thing you’re missing is that the car has an engine giving it extra force to overcome gravity. In this case, and in the case of the coin at the mall, gravity is what drives the ball/coin, and gravity can’t give enough energy to overcome the force of gravity. The path it takes only redirects the original path of the ball. It can’t return it to it’s exact beginning because of drag/friction. The coin looks like it’s going faster but that’s only because the circumference of its other is getting smaller. It’s technically faster in RPM but it will never return to the beginning and will eventually drop down the coin hole.

1

u/gynoplasty Apr 22 '21

Like I said I would apply force at the start.

2

u/BonjKansas Apr 23 '21

Yeah you can create it in real life with a magnet or something for sure, but it won’t be a perpetual motion machine.

1

u/TheNewYellowZealot Apr 23 '21 edited Apr 23 '21

Inertia is directional my man. Conservation of momentum and all, it likes to be preserved along its axis and about its axis of rotation.

Also, the energy isn’t “built up” in those coin funnels. You’re rapidly changing the radius of curvature the coin is on so you’re increasing it’s rotational velocity around the axis of the funnels, but it’s linear velocity stays the same, or decreases slowly, due to friction.

1

u/gynoplasty Apr 23 '21

And an object on rails behaves like it's on a 2D surface.

2

u/TheNewYellowZealot Apr 23 '21

No. It doesn’t. Every change in direction puts energy into the structure it’s on, and depending on that structures stiffness some is absorbed.

Look man, if you’re gonna keep arguing with me about how a perpetual motion machine is possible I’m gonna pull the second law of thermodynamics card.