What happens to the total mechanical energy of the block when it experiences friction while sliding across the floor?

When a block slides across a floor and experiences friction, the total mechanical energy of the block decreases. This reduction in total mechanical energy is primarily due to the work done against friction, which converts some of the block's kinetic energy into thermal energy.

In an ideal, frictionless scenario, a sliding block would maintain its mechanical energy because there are no external forces doing work on it. However, when friction is present, it acts as a non-conservative force, which dissipates energy in the form of heat. The kinetic energy of the block decreases as it continues to slide, and thus the total mechanical energy, comprising both kinetic and potential energy, also diminishes.

Understanding this principle is fundamental in physics, particularly in energy conservation and the effects of non-conservative forces on mechanical systems. Friction is a key factor in real-world applications, and its effects must be accounted for when analyzing the motion of objects.