crunch on *something

chew *something in a gnawing manner / chew *something in a munching manner / chew *something in a crunching manner

scratch (the head)

scratch oneself with a scratching sound / scratch oneself with a rasping sound

trudge along (in *one's studies) / (study) go the grind / hit the book

study grindingly / study drudgingly / <c:figurative> go back to the grind

gal

gal

gal

galvanic action