Making a spinningtop from a metal paper clip

One of my favourite memories of my physics classes at university is of the day when the professor brought in metal paper clips for everybody — to make spinning tops!

When we were playing with the drawing spinning top recently, my mom brought back the paper clip one that I had made some 15 years ago! How is that for a well-organized collection of experimental materials? :-)

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Paper clip and paper clip spinning top

So here is what you do: You unfold the paper clip and turn it into a spinning top! Easy peasy. And if you are keen on all the physics, you can even calculate the angle between the spokes going out from the central axis! 53° or something close is what I remember (and it is confirmed by a quick google search, too). The trick is that the center of gravity has to lie on the rotating axis in the center of the wire that goes around.

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Spinning top made from paper clip

If you want to do this with your students, be nice and hand out the plastic-coated paper clips, they are usually easier to bend. But even with a very imperfect circle and bends that aren’t very sharp or precise, these spinning tops run surprisingly well!

[vimeo 150060319]

Spinningtop trajectories

A new physics toy in my house: A spinning top that has a pen as its tip and leaves trajectories as it spins!

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New drawing spinning top and its trajectory.

The trajectories are really cool. Depending on how you spin the spinning top, they look really different. But they all have a common feature: When the spinning top has slowed down, they end in a long swivel away from all the neat spirals, and in the very end they have the small circle as seen in the top left corner of the picture below.

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Close-up of the trajectory in the photo above

See? The radius of that circle is given by the distance from the tip of the pen to the point on which the spinningtop rests, hence it is the same for all the trajectories. But the rest? The trajectories that are really drawn out were those where the tray on which we were drawing was slowly tilted, so they went away from their point of origin, trying to go downhill.

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Trajectories made by spinningtops.

Now if you don’t have such a spinning top, don’t despair. Use the stub of an old pencil (or of one from your favourite Swedish furniture place), pierce it, tip down, through a circular piece of cardboard, and there you go: Your drawing spinning top is ready!

Watch the movie at the bottom of this post to see this trajectory forming:

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Trajectory made by a spinning top.

[vimeo 150059751]