Although we call the black stuff in pencils “lead,” it’s not the real metal known as lead.It’s actually a mineral called “graphite,” which is made up of carbon. When you write with a pencil, graphite particles from the pencil rub off and stick to the fibers of the paper you’re writing on.
What do erasers do?
When you rub an eraser across a pencil mark, the abrasives in the eraser gently scratch the surface fibers of the paper to loosen the graphite particles. The softeners in the eraser help to prevent the paper from tearing. The sticky rubber in the eraser grabs and holds on to the graphite particles.
Erasers work because of friction.
As the abrasives in your eraser are rubbed against paper, friction produces heat, which helps the rubber become sticky enough to hold onto the graphite particles. As the rubber grabs the graphite particles, small pieces of combined rubber and graphite get left behind. That’s the “stuff” you brush off of your paper when you’re finished erasing.
Everyone knows that a line of standing dominos creates a fun chain reaction when you knock the first one over; but did you know you can use increasingly larger dominos and get the same result?
Professor Stephen Morris knocks over a 1-meter tall domino that weighs over 100 pounds by starting with a 5mm high by 1mm thick domino.He uses a size ratio of 1.5, meaning each domino is one and a half times larger than the last one. This is the generally accepted maximum ratio that dominos can have to successfully knock each other over.
Hans Van Leeuwen of Leiden University in the Netherlands, published a paper online showing that, theoretically, you could have a size ratio of up to two. But that’s in an ideal (and probably unrealistic) situation.
There are 13 dominoes in this sequence. If Professor Morris used 29 dominoes in total, with the next one always being 1.5x larger, the last domino would be the height of the Empire State Building.