Question

an object moves neither up nor down on a horizontal surface. friction and air resistance can be ignored. which of the following statements is true? multiple choice kinetic energy decreases, potential energy increases, and mechanical energy is constant. kinetic, potential, and mechanical energy are all constant. kinetic energy decreases, potential energy is constant, and mechanical energy decreases.

Explanation:

The object moves horizontally (no vertical displacement), so gravitational potential energy (depends on height) is constant. Friction/air resistance are ignored, so no non - conservative forces do work. By the law of conservation of mechanical energy (mechanical energy = kinetic + potential), and since potential energy is constant and no energy is lost, kinetic energy also remains constant. Thus, all three energies are constant.

Answer:

B. Kinetic, potential, and mechanical energy are all constant.