Question

ignoring friction, compare the potential energy of a book on a shelf with the kinetic energy the book will have just as it falls and hits the floor. multiple choice both are exactly the same. they are almost the same but not exactly. the potential energy is greater. the kinetic energy is greater.

Explanation:

According to the law of conservation of mechanical energy (ignoring friction), the total mechanical energy (sum of potential and kinetic energies) of the book - Earth system is conserved. At the shelf, the book has only potential energy. Just as it hits the floor, all of its initial potential energy is converted into kinetic energy. So, the potential energy at the shelf and the kinetic energy just before hitting the floor are exactly the same.

Answer:

Both are exactly the same.