This deceptively simple device can behave in some very unexpected ways. The math and physics behind the movements can be used to explain this behavior.
I am glad that you showed what happens when you raise three or four balls, or one ball on one side and two balls on the other. When we were approaching the end of the video, and this hadn't yet been shown, I was afraid that this was going to be left out.
What if the last two balls were glued together, this will cause them to act as one ball but this also doesn't seem to obey the conservation of kinetic energy?
What if the last two balls were glued together, this will cause them to act as one ball but this also doesn't seem to obey the conservation of kinetic energy?
The conservation laws for momentum and energy are not enough. Take a typical elastic carts demonstration and you can see that the incoming cart (if less massive) rebounds to the right. That is obviously not what Newton's cradle is doing but it is a theoretical possibility based on the two conservation laws. In the case shown (right_one incoming ball), these are possible solutions: right_one stops at 0 v and left_one swings left at -1 v (that's what we see), but also 1 w/ 0.33 v and 2 w/ -0.67 v, 1 w/ 0.5 v and 3 w/ -0.5 v, 1 w/ 0.6 v and 4 w/ -0.4 v. Search for Newton's cradle, "Gavenda", "Simanek", "Hutzler", all of which show that there's more than p and KE to it.
Absolutely love these videos! But, one thing I didn’t find special, in my opinion, was their formula of 1/2mv squared = 1/2mv squared. If you take half of anything multiplied together and square it, it will obviously be the same of what you multiplied before halving it and squaring it. 🤷🏼♂️
hi there. i know this video is a bit old but i just now got one of these. i have loved this toy since i was a kid. i have a question though, do the balls keep on going forever? it seem like mine stops very soon, i hardly get the time to enjoy wathing them. not even 40 seconds playing. thanks.
Hi Yara. How long they bounce depends MOSTLY of the hardness of the balls (Like in real life) lol Most of the cradles out there are realy cheap and have bad balls .... (Also like in real life) So no wonder you hardly could enjoy them .... (You know it)
Next, try the free-falling, "small ball riding on top of a much larger ball when dropped together" experiment. Bouncy rubber balls, hard plastic or metal bearings perform anywhere from great to downright scary (the latter requires safety glasses). Try a triple stack of progressive sizes. Could a top ball ever reach low space orbit, or would it just explode on lift-off? lol
+jmovlogs Good catch! Poor choice of words on my part (orbit). I know it is not possible, but if you try it using baseball size steel bearings, and don't put an eye out in the process, you will see why I took a shot at that high altitude reference. It can be quite violent; glass marbles will explode; steel ones might punch a hole into the drywall ceiling if attempted indoors. Shatterproof safety glasses! Must launch off of massive hard surface, like an anvil. I seem to recall the distinctive sound of the small bearings ZZZzzzzinging by. It could be quite dangerous!
Hello, I'm Davira. I hope you can reply to this comment I think this video is amazing I want to ask permission to use this video for my undergraduate thesis I made a book with additional videos that can be accessed through an application, this video will be included in my application that I made I will still include your channel thanks for your attention
Completely WRONG ! Make a slow motion video of dropping TWO balls, and you will see WHY ! You make the mistake counting the TWO dropping balls as ONE MASS ! Think of it ! In slow motion you can CLEARLY see that dropping TWO balls leads to TWO separate impacts ! THIS is why TWO dropping balls provides to the TWO "escaping" balls and NOT Newtons 3 law !
This does not explain anything. The spheres don't know math or formula's. You just proved that the math holds only in one solution. The better explanation might be found considering multiple spheres as delayed multiple collisions.
What if the last two balls were glued together, this will cause them to act as one ball but this also doesn't seem to obey the conservation of kinetic energy?
On both sides mass of 2 _m_ would move at the speed of _v_. So on the other side one ball with mass of 2 _m_ would move at the speed of _v_. And on the other side 2 balls with mass of 2 _m_ would move at the speed of _v_. That way kinetic energy and momentum would both conserve.
