# How to Keep Your Jenga Tower From Toppling

Fun fact: Jenga, the popular block-balancing game, takes its name from the Swahili word kujenga, meaning “to build.” Swahili is one of the languages ​​that Leslie Scott, the game’s creator, grew up speaking in Africa as a child. Jenga is an apt name considering that even if blocks are carefully removed from a tower, they are just as carefully placed back at the top.

About 95 million Jenga sets have been sold since Ms. Scott introduced it at the London Toy Fair in 1983, according to information extrapolated from her royalty reports. And there are a number of reasons why the game is so popular.

“It’s beguilingly simple (not simple),” Ms. Scott said in an email, “but something really rich and complex (not complicated) happens when people play Jenga. And that is satisfying.”

She added, “It’s tactile and aesthetically pleasing. It’s tense – the tower will inevitably collapse – but you don’t know when, and it can take a surprisingly long time.”

For Crystal Ponti, an author and mother of two who plays the game with her kids, a lot of the fun comes from thinking about why some Jenga towers stay upright and others fall. “I love it when there’s just no explanation as to why the damn thing is still standing,” she said.

Fortunately, the laws of motion developed in 1687 by Sir Isaac Newton – who described the forces acting on a body and the motion of that body – can help demystify the game’s delicate balancing act.

And some of that science can be used to improve the chance of being the last player, so to speak.

Suppose you want to move the middle block from right to left in the graphic below. The forces acting on the block are gravity, normal forces, and frictional forces. Each adds to the complexity of trying to move the block.

A normal power — in this case, “normal” means perpendicular — is a surface where solid surfaces in contact with each other exert forces to prevent them from passing through each other, according to Khan Academy. normal force 1 in the graph pushes down vertically against the top surface of the middle block, and the middle block pushes back. Similar, normal force 2 pushes up vertically against the middle block, and the middle block pushes back.

friction force is the horizontal resistance to sliding motion required to pull the block out and is caused by both the vertical forces pushing against the central block and the horizontal forces influenced by the texture of the blocks. Pushing on a block from the side to remove it also contributes to friction.

Another thing to consider is that while Jenga blocks look the same, not all are the same. Ms. Scott said these anomalies were intentional.

“The game only works as well as it works because each block is unique,” she said. “Each block differs slightly – and randomly – in depth from every other block. This means that the weight of each block is also randomly different.”

She added: “It also means that every move made is unique and practically unpredictable.”

A basic knowledge of these powers can help players the next time they are challenged to a game. Here’s how to use them to your advantage.

Players can only remove blocks below the top two rows, but you can select a block somewhere else. A block near the top has less weight, meaning the downward normal force is slightly weaker. This makes it easier to move the block.

Because of the difference in size, the blocks don’t lie perfectly flat on top of each other. So removing blocks can be a challenge, but a player with a keen eye can have an advantage.

“The variations in size and shape have a big impact on friction,” said Steve Langer, a Chevy Chase, Md. physicist, in an email seeking comment. “Sometimes you can see if a block is looser than the others and easier to remove.”

The rest of the tower above this middle block is still supported by the blocks on either side of the row. If tip #2 applies to the center block – which means it’s not as thick as those on either side – even better.

An obvious tip would be to keep the hand used steady and gently move the selected block horizontally. But even paying attention to the block above can mean the difference between a successful move and a resounding crash.

Joon Pahk of Somerville, Mass., is a former Harvard physics teacher. “The way the tower topples over,” he said in an email, “generally is that the block in the plane above the moving block also starts to slide.”

In other words, the weight of the block on the one you want to move matters. If the block you want to move carries a thicker one, that weight will increase the frictional forces exerted on the selected block. You might want to move another block for now.

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The rules of the game allow for a little tapping at first to see if a block is loose, but after that, Mr. Pahk suggests applying steady pressure.

“The force required to start gliding is slightly greater than the force required to maintain gliding,” he said. “You’re trying to minimize all those horizontal forces, because those are the ones that are shifting the blocks over what you’re sliding on.”

Players need to put their blocks back on the tower, and putting them in the wrong places can cause instability. When a side block is pulled, the vertical forces push the blocks above it further down, also across the gap that has now arisen.

One way to reduce the effect of these forces is to place the removed block on the opposite side of the tower, as long as there is more than one block to support the weight. Therefore, if a block is removed on the right side of the tower, it is better to place it on the left.

If a center block is your only choice, we wish you the best of luck. But it can be done.

If a block is stuck to the side, players can “wiggle” it out by swinging one end of the block out like opening a book. Gently rocking the end of the block in and out can help loosen it — and can also move the block closer to the edge.

Just kidding. But look at the style of this very good dog!

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