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.

Materials scientists are measuring the rolling friction of tiny, micrometer-sized particles. These measurements permit them to better understand everyday products such as concrete.

Earlier, we saw that the work done by friction on a particle sliding on a rough surface is negative, causing a loss in total mechanical energy as the particle slides. Here, we will address the ...

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 ...