How does a Ballpoint Pen work?

A ballpoint pen uses a tiny ball to help ink flow onto paper.

Imagine you have a small ball inside your pen, like a marble. This ball is covered in ink, and when you write, the ball rolls on the paper. As it rolls, it carries the ink with it, leaving a line behind. It’s just like when you roll a wet paintbrush across a canvas, the paint moves along with the brush.

When you press down on the pen, the ball starts to move. The more pressure you use, the faster the ball rolls. This means more ink comes out and makes your writing darker. If you write lightly, the ball rolls slower, so less ink is used, like when you tap a paintbrush gently on paper.

The ink inside the pen is thick, like syrup. Because it’s not runny, it doesn’t spill out all over your hand unless you shake the pen really hard, just like how syrup stays in a bottle unless you turn it upside down.