That is a very sharp knife, excellent of course for peeling potatoes. But it’s excellent for something else as well… Put the knife in the paper on top of the potato and then press. Surely it’s going to cut its way through the paper and then through the potato.
What do you think will happen?
In this old clip from Australia’s Curiosity Show, now on YouTube, science educator and co-host Rob Morrison demonstrates how you can cut through a raw potato without cutting through paper between them, even though the knife is very sharp.
In the clip below, Morrison pushes a paper straw through a raw potato… but he needs to make a few quick fixes to the straw first. Watch as he fails, makes adjustments, and succeeds at this classic experiment.
This potato physics trick is sometimes accomplished by covering the end of a plastic straw with your thumb, but it’s more impressive with a more sustainable paper straw. Who would think that a crushable paper cylinder can be jabbed all the way through a hard potato? An explanation from KiwiCo:
A neat thing about gases (like air) is that when they get squished, they transfer that squishing pressure to their containers. A squished gas has less space to move in, so the gas bounces around its container faster and harder. If you’ve ever squeezed a balloon and seen it bulge out, you’ve seen air pressure at work. In this experiment, the air inside the straw gets squished (and pressurized) when you jam the straw into the potato. The squished air pushes out on the sides of the straw and keeps the straw from bending — that’s the power of air pressure!