People often brag about Large Hadron Collider as having one of the most sophisticated Technology in the world. True, but even if you are living in France, it’s still inaccessible! I believe that accessibility is the true trait of technology.
Look around the place that you are sitting in. Do you see a Ball Point pen lying around in the vicinity? Chances are that it is, are really high. Today on FYP, we will unravel the modest physics that governs it.
Behold the ball in a ball point pen!.
To write you glide your pen onto the paper right? So what you are doing is rolling the ball that is present on the pen’s tip.
The ink flows continuously under the influence of gravity from the ink reservoir to the ball.
The ball rolls and the ink gets transferred onto the paper.
How does the ink stay inside the pen?
Put a drinking straw into a glass of water (or any liquid) and then put your finger over the top end of the straw so it’s air tight. You can now lift the straw out and the liquid will not fall out of the straw!
Now switch characters and imagine the liquid to be the ink and the straw to be the ink reservoir and voila!
Rollerball pen and Ballpoint pens work on the same principle. They differ in the type of ink used. While Ballpoint pens have a thicker oil based ink, the rollerball uses a liquid ink, thus giving its fluidity.
(Sources : http://home.howstuffworks.com/pen3.htm )