Friction is a force between two surfaces that are sliding, or trying to slide, across each other. For example, when you try to push a book along the floor, friction makes this difficult.

They’re using a linear friction welding machine which oscillates the sample at about 200hz. Their best guess is linen lignin cells within the wood are melting, interlocking and rejoining ...

We might naively expect rough surfaces to show greater friction, for example, yet it is sometimes higher between perfectly smooth and molecularly clean surfaces. More surprising, friction can ...

Imagine a heavy book resting on a table. If you try to gently push the book across the table with the tip of your finger, it ...

To me, it represents another example of shifting work to the customer while adding new forms of friction to the shopping experience. Self-checkouts, anyone? Anyone who has tried to buy razors ...