Nail assembly

With the right weight distribution, it’s possible to balance six nails on just one!

A plate with two half potatoes into which nails have been inserted

Step 1

Start by placing the potato on the table with the flat side facing down. Push a nail into the rounded side, so it stands upright and stable.

Tip: check that the nail is perfectly straight. If it leans even a little to one side, the experiment won’t work.

A plate with two half potatoes and nails inserted into it on which a nail is balanced

Step 2

Now, see if you can balance the six remaining nails on the single upright nail. It’s not easy, but there is a way. Can you figure it out?

Tip: Create a stable structure with the six nails before attempting to balance them on the standing nail.

5 nails laid out in the shape of the letter H

Step 3

The secret is to stack the six nails in a clever pattern on the table first. Here’s how you do it:

Start by placing one nail flat on the table. This is your ‘base nail’. Then, take four more nails and lay them across it. Position two nails at each end so that their heads slightly overlap the base nail.

Tip: You should now have five nails on the table, arranged like the letter H.

A girl lifts 5 nails hanging from each other

Step 4

You’ve still got one nail left. Place this nail on top of the base nail, pointing in the same direction, but with the nail head on the opposite end.

Hold both ends of the base nail and the last nail firmly, and lift. The whole structure should come up!

A plate with two half potatoes into which nails are inserted on which 6 other nails are balanced

Step 5

Carefully position your nail assembly on top of the upright nail, making sure the centre point rests perfectly on the nail head.

What did you discover?

All objects have a centre of gravity – the point where the weight is evenly balanced. For simple shapes, like a tennis ball, it’s right in the middle. But a nail is long and has a heavy head, so its centre of gravity isn’t in the centre but rather off to one side.

In your nail assembly, all the weight is evenly spread out, which brings the centre of gravity to the middle. And because the centre of gravity is right in the middle, the structure stays perfectly balanced.