In December of 1989, a KLM Boeing 747 airplane carrying 231 passengers entered a cloud of ejecta from an Alaskan volcanic eruption. All four engines went out, and the plane fell from 27800 ft to 13700 ft before the engines could be restarted. It then landed safely in Anchorage. Neglecting any air resistance and aerodynamic lift, and assuming that the plane had no vertical motion when it lost power, (a) for how long did it fall before the engines were restarted, and (b) how fast was it falling at that instant?
