Final answer:
When a cardboard box is pushed across a carpeted floor, the interactions between molecules in the cardboard and carpet produce heat. This heat is generated due to the frictional force generated between the two surfaces. The kinetic energy from the movement of the molecules is converted into thermal energy, leading to the warmth felt on the bottom of the box.
Step-by-step explanation:
The warmth felt on the bottom of the cardboard box after it was pushed across a carpeted floor is due to the interactions between molecules in the cardboard and molecules in the carpet. When the box is pushed, frictional force is generated between the two surfaces. This friction causes the molecules in the cardboard and carpet to move and vibrate, producing heat as a result. The kinetic energy from the movement of the molecules is converted into thermal energy, which is why the bottom of the box feels warm.