How to Make a Newton's Gravity Puzzle

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About: My name is Troy. I'm a Mechatronics graduate studying Mechanical Engineering. I like to make things and spend time outdoors (especially SCUBA diving). I am a Community Manager for Instructables.

The Newton's Gravity Puzzle is a very simple puzzle. The objective is to remove the center piece while keeping the puzzle on a level surface. No tools can be used to remove it, only your body and the puzzle itself.

Here are the steps to make your own puzzle along with the solution at the end.

Step 1: Tools and Materials

Materials:

  • Wood
  • Paint

Tools:

Step 2: Inner Piece

This inner piece of the puzzle is made from an old cedar 4x4. However, any light would work here. I mounted it in the nova chuck and turned a cone on the end then turned it round to a diameter of 1 in.

Remove the piece from the lathe without parting it off.

Step 3: Turn the Outer Shell

Turn the shell between centers then mount it in the nova chuck. Hollow out the center just larger than the inner piece. You want between 1/16 and 1/8 inch of clearance all the way around. This hole should be about 1 1/4 in. deep. Once the hole is at the correct depth, turn to the final diameter of 1 3/4 in and add a chamfer to the edge if you like.

Part it off at a length of about 1 1/2 in.

Step 4: Cut the Inner Piece to Length

Once the shell is parted off, you want to cut the inner piece to the correct depth. The edge of the inner piece should be just below the shoulder of the shell. It should sit low enough in the shell that the inner piece can't be grasped with fingernails.

Step 5: Sand and Paint

Sand and apply any color paint you like. I went with the traditional red of the original Newton's Gravity Puzzle.

Step 6: How Does It Work?

Atmospheric pressure is present around every object on earth. The Newton's Gravity Puzzle is solvable through creating a difference in pressure above and below the inner piece. To overcome the acceleration of gravity, a gentle blow directly on the puzzle will decrease the pressure above the cylinder sucking it out and solving the puzzle.

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    21 Discussions

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    Bill WW

    23 days ago

    Great, Troy. I'll make some for the grandkids - and their parents for Christmas.
    From one mechanical engineer to another: if you have had your fluid dynamics courses, you know Newton had little to do with this. The puzzle is best explained by Bernoulli's equations, and demonstrated by an airplane wing - the moving air over the curved top of the inner part creates a lower pressure and lifts it out of the shell.

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    tomatoskinsBill WW

    Reply 21 days ago

    Haha I'm actually currently finishing up my first fluid dynamics course right now (3 weeks left!). I hadn't actually thought about it in terms of Bernoulli's equations. But you are completely right!

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    kayakdivertomatoskins

    Reply 2 days ago

    Half right, in a way... Newton is keeping it down, and Bernoulli is lifting it up. Those two have been at odds (mostly) since the days of Icarus! Cool little trick toy!

    An enhancement might be to (perhaps secretly) hollow the plug to lighten it. And, I wonder if a less pointed top would create a better air foil providing more adhesion (less stall or "spoilage") of the air to the surface.

    It would be cool if the viewer didn't see you blowing on it when you demonstrate it.

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    Bill WWkayakdiver

    Reply 1 day ago

    Thanks Kayak, you reminded me to get busy and make a couple of these for grandkids this Christmas. You and I are on the same wavelength: hollowing the plug to lighten it. And I will experiment on my lathe to make various airfoils.

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    kayakdiverMathiasE5

    Answer 2 days ago

    I would suspect that you work just about anywhere outside of North America, the UK, or possibly Japan. I think it is generally agreed that a purely decimal based measurement system ultimately makes more sense and is (or would be) easier to work with than the seemingly arbitrary inches, feet, miles, etc. (as well as ounces & pounds Vs. grams) we use and are way more accustomed to. With that said, neither is more precise; just add a couple of decimal places to get to the precision you desire. Woodworkers alone, however, might argue this doesn't apply when working in 64ths, 32nds, 16ths, 8ths, etc. of an inch.

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    tomatoskinsMathiasE5

    Answer 7 weeks ago

    You can easily convert the few measurements from in. to mm by multiplying by a factor of 25.4.

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    JohnSmith-Workshop

    22 days ago

    It's a really mindblowing puzzle. When I read the whole thing i was amaized how simple it is. Awesome job mate :D

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    JT Woodworks

    5 weeks ago

    This is so cool!! Great way to teach physics to children

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    Arbormakes

    6 weeks ago

    This is so cool. I do not have the cutting tools to make it but I know that it is amazing.

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    DawsonC10AndrewH345

    Reply 7 weeks ago

    If I had to guess it’s just any light wood (weight wise) to make it easier for the inner peice to lift out. But I could be wrong

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    tomatoskinsmacwiley

    Reply 7 weeks ago

    That looks great! Were you able to print it yet?

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    macwileytomatoskins

    Reply 7 weeks ago

    Thank you, and yes, I did. I'll post a photo of it after my wife brings it back from work.

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    Alex in NZ

    7 weeks ago

    A beautiful little trick/toy/experiment. Thank you for sharing it :-)

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    Build-Bot

    7 weeks ago

    This is really cool!
    Nice job, tomatoskins!

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    ynze

    7 weeks ago

    Ooooww, wonderful!