Explain Kinetic Energy Changes Practice Test

Friction acts opposite the motion, so it does negative work and converts some of the book’s kinetic energy into thermal energy.

Friction acts in the same direction as the motion, so it does positive work and increases the book’s kinetic energy.

The book slows down because its mass becomes smaller as it slides, lowering its kinetic energy.

The book slows down because its kinetic energy is being converted into more kinetic energy.