Mechanical Energy
Mechanical Energy - Related Videos
01:05
Conservation of Mechanical Energy
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2023
The mechanical energy E of a system is the sum of its potential energy U and the kinetic energy K of the objects within it. What happens to this mechanical energy when only conservative forces cause energy transfers within the system—that is, when frictional and drag forces do not act on the objects in the system? Also assume that the system is isolated from its environment; in other words no external force from an object outside the system causes energy changes inside the system. When a...
04:10
What is Energy?
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2020
The universe is composed of matter in different forms, and all forms of matter contain energy. The different forms of energy on Earth originate from the Sun — the ultimate energy source. Plants capture light energy from the Sun, and, via the process of photosynthesis, convert it into chemical energy. This stored energy from plants can be harnessed in many ways. For example, eating plant products as food provides energy for our body to function, and burning wood or coal (fossilized plants)...
08:52
Energy and Work
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2023
Source: Ketron Mitchell-Wynne, PhD, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA This experiment demonstrates the work-energy principle. Energy is one of the most important concepts in science and is not simple to define. This experiment will deal with two different kinds of energy: gravitational potential energy and translational kinetic energy. Gravitational potential energy is defined as the energy an object...
02:39
Gibbs Free Energy
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2020
One of the challenges of using the second law of thermodynamics to determine if a process is spontaneous is that it requires measurements of the entropy change for the system and the entropy change for the surroundings. An alternative approach involving a new thermodynamic property defined in terms of system properties only was introduced in the late nineteenth century by American mathematician Josiah Willard Gibbs. This new property is called the Gibbs free energy (G) (or simply the free...
01:21
Free Energy
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2019
Free energy—abbreviated as G for the scientist Gibbs who discovered it—is a measurement of useful energy that can be extracted from a reaction to do work. It is the energy in a chemical reaction that is available after entropy is accounted for. Reactions that take in energy are considered endergonic and reactions that release energy are exergonic. Plants carry out endergonic reactions by taking in sunlight and carbon dioxide to produce glucose and oxygen. Animals, in turn, break down the...
FAQs
Mechanical energy remains constant only when the system is influenced by conservative forces alone. Under that condition, a decrease in one form is balanced by an increase in another, allowing motion to be predicted without separately tracking a net loss. The conservation rule therefore provides a direct test for idealized physics models.
During a change in motion or position, energy can shift between kinetic and potential forms. For example, a pendulum, roller coaster, or spring system can exchange energy between motion and stored energy as its conditions change. Tracking this exchange helps explain why speed may vary even when total mechanical energy stays unchanged.
Friction and air resistance alter the mechanical-energy balance by transferring part of it into thermal energy. Consequently, the mechanical total need not remain constant even though energy is not simply disappearing. Including these effects is important when interpreting real motion, because an ideal conservative-force calculation can otherwise overestimate the energy available for movement.
To analyze mechanical energy in a physics problem, first identify the system and describe its motion, position, or configuration. Then distinguish the kinetic and potential contributions, follow how they convert, and determine whether conservative forces, friction, or air resistance act. This workflow supports predictions of motion and reveals whether thermal transfer must be included.
Mechanical energy analysis is useful for systems whose behavior changes over time, including pendulums, roller coasters, springs, and planetary orbits. In each case, comparing motion-related energy with energy associated with position or configuration can clarify the system’s evolution. The same reasoning also helps evaluate machines by linking changing conditions to expected motion.
Within physics, the principle connects ideal models with practical systems. A conservative-force model treats total mechanical energy as constant, while a model that includes friction or air resistance accounts for transfer to thermal energy. Comparing these descriptions helps students and researchers decide which assumptions fit a problem and how closely predictions should represent actual behavior.