Basically, a passive radiator is a reactionary device as the name suggests. When a driver (such as a subwoofer) is mounted to a sealed speaker box (enclosure), the physical forward/back movement of the speaker affects the internal air pressure of the enclosure.
Three landforms created by wind are; sand dunes, yardangs (half-teardrop shaped formations hill sized, and deflation hollows (wind swept depressions.
Landforms created by erosion. The coastline is constantly eroding. There are four key types of erosion: 1  Abrasion-waves transport material which hit the cliff and gradually wear it away. 2  Hydraulic action-as waves approach the coast they trap air and force it into gaps in the cliff. 3  Eventually this weakens the rock.