Friction friction and wear in so-called self-lubricating materials. Fluid friction occurs between fluid layers that are moving relative to each other. This internal resistance to flow is named "viscosity". In everyday terms, the viscosity of a fluid is described as its "thickness". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity. The less viscous the fluid, the greater its ease of deformation or movement. All real fluids (except superfluids) offer some resistance to shearing and therefore are viscous. For teaching and explanatory purposes it is helpful to use the concept of an inviscid fluid
What Is to Be Done? (Tolstoy) the same Biblical reference (Luke 3:10–14). What Is to Be Done? (Tolstoy) What Is To Be Done? (sometimes translated as What Then Must We Do?) is a non-fiction work by Leo Tolstoy, in which Tolstoy describes the social conditions of Russia in his day. Tolstoy completed the book in 1886, and the first English language publication came in 1887 as What To Do?. A revised translation with the current title was published in 1899. The English title was also used for two better-known works by Nikolai Chernyshevsky and Vladimir Lenin; Tolstoy's Russian title is similar but not identical to Chernyshevsky's