Question

Define mechanical energy. What is the relationship of mechanical energy to nonconservative forces? What happens to mechanical energy if only conservative forces act?

a) Mechanical energy is the sum of kinetic and potential energy; it is conserved in the absence of nonconservative forces.
b) Mechanical energy is the energy of machines; it is unaffected by nonconservative forces.
c) Mechanical energy is the energy of motion; it decreases in the presence of nonconservative forces.
d) Mechanical energy is the energy of gravity; it is unaffected by conservative forces.

Answer 1

Mechanical energy is the sum of kinetic and potential energy in a system. It remains conserved when only conservative forces act, but can change if nonconservative forces like friction do work on the system. Therefore, the correct answer is a) Mechanical energy is the sum of kinetic and potential energy; it is conserved in the absence of nonconservative forces

Step-by-step explanation:

Mechanical energy is defined as the sum of kinetic and potential energy in a system. When only conservative forces act on a system, the mechanical energy remains constant; however, if nonconservative forces, such as friction or air resistance, are present, they do work that alters the mechanical energy of the system.

This is because work done by nonconservative forces changes the kinetic energy (KE) and/or potential energy (PE) of the system.

Mechanical Energy with Only Conservative Forces

When a system is only influenced by conservative forces, its mechanical energy stays conserved. This implies that the total mechanical energy (kinetic plus potential) at one point in time is equal to the total mechanical energy at any other point in time. Conservation of energy dictates that energy may change form, but the total mechanical energy remains unchanged.

In summary, mechanical energy will be conserved in the absence of nonconservative forces, whereas the presence of nonconservative forces will result in a change in mechanical energy.