Powder
In nature, dust, fine sand and snow, volcanic ash, and the top layer of the lunar regolith are also examples.Typically, a powder can be compacted or loosened into a vastly larger range of bulk densities than can a coarser granular material.The clumping behavior of a powder arises because of the molecular Van der Waals force that causes individual grains to cling to one another.Only when the grains are very small and lightweight does the Van der Waals force become predominant, causing the material to clump like a powder.These include segregation, stratification, jamming and unjamming, fragility, loss of kinetic energy, frictional shearing, compaction and Reynolds' dilatancy.For one thing, tiny particles have little inertia compared to the drag force of the gas that surrounds them, and so they tend to go with the flow instead of traveling in straight lines.Mechanical agitation such as vehicle traffic, digging or passing herds of animals is more effective than a steady wind at stirring up a powder.
Powder (disambiguation)Powders (album)fine particlesflow freelygranular materialsgranulargrain sizesform clumpscoffeepowdered milkgunpowdercosmeticpharmaceuticalsvolcanic ashregolithchemical engineersmechanical engineerschemistsphysicistsgeologistsbulk densitiesVan der Waals forcefragilitykinetic energyfrictionalcompactionReynolds' dilatancysilicosissuspendedturbulencedust stormsmudstonecohesivePneumaticfluidized bed combustiondustinessDust explosiontitaniumcohesionliquidangle of reposeshear stressesFragile matterGranular materialLiquefactionGrain sizePaste (rheology)Powder mixtureBagnold, R.A.Routes of administrationdosage formsDigestive tractenteralSolidsTabletCapsulePastilleTime release technologyOsmotic delivery systemLiquidsDecoctionElixirElectuaryEmulsionEffervescent powder or tabletHerbal teaHydrogelMolecular encapsulationSoftgelSolutionSuspensionTinctureOral mucosabuccalsublabialsublingualOrally disintegrating tabletSublingual dropsLozengesEffervescentChewing gumMouthwashToothpasteOintmentRespiratory tractinhalationDry-powder inhalerSmokingAnesthetic vaporizerHeated humidified high-flow therapyMedical inhalantsMetered-dose inhalerNebulizerVaporizerOxygen maskNasal cannulaOxygen concentratorAnaesthetic machineRelative analgesia machineOphthalmicNasal sprayEar dropsEye dropsInsufflationMucoadhesive microdiscUrogenitalPessaryVaginal ringDoucheIntrauterine deviceExtra-amniotic infusionIntravesical infusionRectalSuppositoryMurphy dripNutrient enemaDermaltopicalTopical creamTopical gelLinimentIontophoresisLiposomesTransfersome vesiclesLotionLip balm