Penny was sent home from class for being disruptive in physics class. She berated her instructor for being unaware on the emerging Physics Of Chaos. Veronica, her iron handed governess, thought Penny needed further instruction in the Laws Of Thermodynamics and unleashed an entropic reaction upon her bottom with the bath brush.
As the bath brush was landing upon her exposed and red bottom, Penny discovered that Veronica had a firm grasp of scientific principals, too. A bath brush falling upon her bottom will generate both heat and sincere, yet desperate, promises to be respectful of her elders.