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.
Desert landforms. You must understand that a process is what creates a landform. A landform is a distinct feature in a landscape. At the most basic, you must be able to describe the processes that lead to the formation of a rock pedestal and a barchan dune (a crescent shaped sand dune).