# In this pendulum wave video (in details) by how much do the balls slow down with each arc?

Asked by Dutchess_III (34040) February 28th, 2014

Here

Seems like I remember reading or hearing that it slows down by X amount each time, but I can’t remember what X is.

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This is a @PhinotPi question.

Seek (34342)

Aaaand…there he is. Thanks for answering.

Dutchess_III (34040)

Does this description sound familiar to you?

I’m not sure if this is what you are talking about, but it does give the speeds for each of the pendulums. The longest pendulum swings 51 times in one minute, while each shorter pendulum makes one additional swing each minute. The shortest pendulum swings 65 times in a minute. The speed of the individual balls does not decrease over time., as the pendulums are still swinging as quickly at the end of the video as they are towards the beginning.

PhiNotPi (12609)

But they do eventually come to a stand still. Therefore they must be slowing down incrementally, right? They won’t swing for all eternity. Let me go look again.

Dutchess_III (34040)

And thanks for the link.

Dutchess_III (34040)

Husband, “Val, why are you drawing a line on the computer screen with white out?”
Me, “Mumble mumble PhiNotPi mumble mumble….”

Dutchess_III (34040)

OK, just keeping my eye on the longest one, nearest at me, when it first starts out, about half if it is hidden behind the left leg (facing me) on the stand at the height of it’s arc. At about 1:11 it is no longer swinging behind the metal leg at all, so it’s slowing down. I know it slows down, they ALL slow down at a particular rate. What is that rate on earth?

Dutchess_III (34040)

Maybe I’m asking the question wrong….

Dutchess_III (34040)

@PhiNotPi

I believe she’s asking about the decrease speed rate. Like, if you jumped off a tree limb holding a rope, how many swings would it take for you to be hanging like a loser over the lake because you’re too scared to jump?

Seek (34342)

It just hit me. It isn’t “slowing down.” It’s losing energy (I’m watching The Nutty Professor against my will. Good movie for stimulating the brain not.) OK, so they’re losing energy, but they’re all losing energy at the same rate.
What is that rate?

Dutchess_III (34040)

It is not true that all pendulums lose energy at the same rate. It depends on many factors, such as air friction. There is something called the Q factor which measures the energy loss in oscillating devices.

PhiNotPi (12609)

OK, what about in the link I posted. All of the balls are exposed to the same factors, aren’t they?

Dutchess_III (34040)

Well, longer pendulums have lower speeds simply by their length. The “waves” which seems to travel and reverse direction are an illusion caused by the different speeds of the different pendulums.

PhiNotPi (12609)