rack, wrack

As a noun or verb rack is associated with pain, torment, or twisting and straining, and with any sort of framework, including the instrument of torture:

            Roger confessed on the rack

            nerve-racking trip

            rack one's brains

As a noun or verb wrack is associated with wreckage or destruction:

            wrack and ruin

            storm-wracked coast

            wind wracked the vessel