LEGO plus Slinky = Physics

What happens when your kids won't give you a turn on the Wii? Simple. You take their LEGO bricks and their slinky and do some physics. I will keep this simple. Basically, I created a slinky holder out of LEGO pieces and added LEGO bricks to the end to stretch it. Here is the video.

Lego + Slinky = Physics from Rhett Allain on Vimeo.

Maybe in an un-Dot Physics fashion, I am not going to analyze this data. I am not going to even describe the physics. Instead, I will leave this as a What Can You Do With This in the style of Dan Meyer.

I will give a couple of hints. First, I put this on vimeo because there you can easily download the video (look in the lower right)


Second - if you want to analyze the video, or take measurements, I recommend Tracker Video for video analysis.

One more thing, here is a bonus video.

Oscillating LEGO bricks on a slinky from Rhett Allain on Vimeo.

Feel free to analyze that, but there may be a problem. Hint 2: the mass of the LEGO bricks is small. That is all I am going to say.

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Hooke's law?

By Alex Besogonov (not verified) on 28 Dec 2009 #permalink

Dang, so you're telling me that my fancy store-bought Hooke's Law experimental springs and slotted mass sets could have been replaced with Slinkies (Slinkys?) and Lego blocks?! I like it, and maybe I'll play around with it for next year's experiment in my Algebra classes (we've already done it this year).

I'll go with Hooke's law as well. However, my eyes couldn't see the video well enough to calculate the spring constant in terms of bricks per brick, or even verify that it was linear.

But I prefer LEGO + Slinky - LEGO = Physics.

There's all the fantastic wave stuff you can do with a slinky by taking advantage of the fact that it isn't massless (as you hint at in video 2). Transverse waves! Longitudinal waves! Standing waves! Different normal modes! Inversion on reflection! (And noninverting reflections, depending on how you fix your slinky end). But then again, I'm more of a waves guy than a particle guy, so any time I see a slinky I start salivating for waves physics.

By Anonymous Coward (not verified) on 28 Dec 2009 #permalink

One solution to the problem is to get Lego Indiana Jones which allows multiple players.


Good idea - too bad there are more kids than controllers. Actually, I was just looking for an excuse to blog.

Lemme ask you, Rhett: what changed? Any specific reason you decided not to do your usual thing with this one, posting diagrams and formulas and what-not, all up front?


Here is what changed, in descending order of importance.

1) I am not really at work right now - if you know what I mean. Adding all the explanations sure would make that post take a longer time.

2) I have kind of done this explanation thing before, so maybe I should try something different.

3) I thought this would be useful for some classes to use as a project. If I explained the whole thing, that would kind of ruin it for everyone.

4) I was just trying to get your attention.

I love this! Two data points for the period aren't exactly optimal, but that might be enough to figure out the mass of the spring from the period with everything in "block units", since you change the "M" by a big step to help with the non-linearity.

That means your next posting should be a photo of a Lego balance that is being used to weigh the slinky against the Lego blocks used to make the oscillator.

Hint3 to newbies: spring mass/3.

By CCPhysicist (not verified) on 29 Dec 2009 #permalink