Why is there a small hole in the plastic seat, not another?

The plastic chair is so familiar with our daily lives. There is also a round hole in every chair, we still use it when we need to use a plastic chair, but not many people question its existence.

So why should there be a hole in a plastic chair?

Why is there a small hole in the plastic seat, not another? Picture 1

If asked this question, surely many people will give the answer: to be easy to handle, easy to transport. This has to be the most accurate answer to this question.

In fact, the purpose of appearing manufacturers' holes is related to air pressure. If there is not a hole in the seat, then putting pressure on the air will make them stick together so it is difficult to disassemble each piece and it is difficult to stack neatly and firmly.

This reminds us of the physics experiment " Magdeburg hemisphere " that was previously studied. 16 horses, divided into two groups, pulled with all their strength and still could not separate the two hemispheres of copper and fit together and sucked in the air inside.

Although the space between the two chairs folded together does not create a vacuum environment but before being pulled out, the pressure between the two chairs will decrease, creating a similar effect. Therefore, an opening is needed to lose this effect.

Why is there a small hole in the plastic seat, not another? Picture 2 Seat side air vents help protect against vacuum effect.

But why should it be a circular hole but not a square or a rectangle?

For square holes, or any other angular shaped hole, most of the pressure is concentrated at the edge. So when under pressure it will easily crack, affecting the durability of the seat and the safety of the user.

Why is there a small hole in the plastic seat, not another? Picture 3

Why is there only one hole? A hole is not big, not small enough to ventilation. If the hole is too big, it will affect the strength of the structure causing the chair to be weakened and easily broken. If the hole is too small, our fingers will not fit and make it difficult to use.