Energy

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Energy

Energy is the capacity of a force to generate action or work. Any force that does work on an object causes a change in its energy.

In physics, we refer to energy as the capacity of a system or phenomenon to perform a given work. The word energy comes from the Greek enérgos, meaning "force of action" or "work force." It is a widely used concept in this science and in other sciences in general, with diverse meanings and interpretations.

This ability to perform work is key to physics' interest in energy, since this discipline studies natural systems as actions and reactions in which matter interacts and energy is transferred from one system to another, from one form to another.

In fact, energy is governed by the Second Law of Thermodynamics, which establishes that the amount of energy in the universe is always stable, permanent, and can neither be created nor destroyed, only transformed.

On the other hand, in relativistic mechanics, governed by Albert Einstein's Theory of Relativity, energy and mass have a relationship. narrower than that defined by the famous equation E = m*c2, that is, energy equals mass times the speed of light squared. Thus, all bodies, simply by being composed of matter, possess a quantity of energy given by Einstein's equation.

On the other hand, energy (E) and work (W) are equivalent, so they are measured in the same type of units: Joules (J), that is, Newtons per meter (N/m).

Potential Energy

Potential energy is associated with a given body or physical system by virtue of its position or height, that is, based on a force field in which it is immersed. This type of energy can be classified as:

Gravitational potential energy: This is the energy possessed by a massive body when immersed in a gravitational field. Gravitational fields are created around objects with very large masses (such as the masses of the planets and the sun).

For example, a roller coaster car has maximum potential energy at its highest position because it is immersed in the Earth's gravitational field. Once the car drops, it loses height, and the potential energy is transformed into kinetic energy.

g is the acceleration of gravity measured in meters per second squared. (m/s2)

Example: What is the potential energy of an object that is at a height of 20 meters, if it has a mass of 10 kilograms?

Electrostatic potential energy: In the field of electricity, the concept of potential energy also applies, which can be converted into other forms of energy, such as kinetic, thermal, or light, given the enormous versatility of electromagnetism. In this case, the energy results from the electric force field produced by the charged particles.

Example: What is the potential energy of an object that is 20 meters high if it has a mass of 10 kilograms?

Elastic potential energy: Elastic potential energy has to do with the property of elasticity of matter, which is the tendency to return to its original shape after being subjected to deforming forces greater than its resistance.

A clear example of elastic energy is the energy possessed by a spring that stretches or contracts due to the effect of an external force and returns to its original position once that force is no longer applied.

Another example is the bow and arrow system. In the latter, elastic potential energy reaches its maximum value as the bow is drawn taut by pulling on the elastic fiber, bending the wood slightly, but still at zero velocity. The next instant, the potential energy becomes kinetic energy, and the arrow is propelled forward at full speed.

Chemical Potential Energy: Chemical potential energy is the energy stored in the chemical bonds of atoms and molecules. An example is glucose in our body, which stores chemical potential energy that our body (through a process called metabolism) transforms into heat energy to maintain body temperature.

The same thing happens with fossil fuels (hydrocarbons) in a car's gas tank. The chemical potential energy stored in the chemical bonds of gasoline is converted into mechanical energy to power the vehicle.

Kinetic Energy

Kinetic energy is the energy of motion, and is often designated by the symbols K, T, or Ec, as it is extremely important in various fields of physics. A body moving at a given speed will have an associated kinetic energy.

Kinetic energy is key to the concept of temperature; in fact, temperature is the kinetic energy of the particles that make up a substance or object.

The traditional formula for calculating the kinetic energy of a body moving at a speed (v) is as follows: Ec = ½ * m * v2

Example: Calculate the kinetic energy of a 65 kg person walking at a speed of 1.2 m/s.

Force

In physics, force is a vector magnitude that is capable of modifying the momentum or shape of a given body or material. It is not equivalent to effort or energy.

Force is measured in the International System using Newtons (N). A Newton is defined as the amount of force required to accelerate an object of mass 1 kg by 1 m/s2.

Work

In Newtonian (classical) physics, the work of a force is defined as the product of the force and the distance over which that force is applied.

This work is equivalent to the amount of energy required to accelerate the movement.

Work is represented by the symbol W; it is a scalar quantity (without direction) and is expressed in the same units as energy J.

It is calculated as the product of the applied force and the distance traveled in the direction of the force (W = F * d).

Activity. Answer the following questions.

Remember to check the answers to the open questions at the bottom of this page..

1. Which of the following statements is correct about kinetic energy?

2. Chemical potential energy is stored in:

3. What form of energy is converted when a spring is compressed and then returns to its original shape?

4. What type of energy is released when gasoline is burned in a car?

5. According to the Second Law of Thermodynamics, the energy in the universe:

Once you click this button, the questions will close and you will not be able to change your answer.

6. What is work in physics and how is it calculated?

7. Explain what chemical potential energy is.

8. A 10 kg object is 5 meters high. What is its gravitational potential energy? (g = 9.8 m/s²)

9. An 800 kg car moves at a speed of 20 m/s. What is its kinetic energy?

10. A 15 kg object moves at 3 m/s. What is its kinetic energy?

Still have questions?

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Answer to open questions:

6. Work in physics is the amount of energy transferred by a force acting on an object over a distance.

It is calculated as the product of the applied force and the distance traveled in the direction of the force (W = F * d).

7. hemical potential energy is the energy stored in the chemical bonds of molecules.

9. 1,600 Joules | Ec = 1/2 * m * v2 | Ec = 1/2 * 800 * (20)(20) | Ec = 1/2 * 800 * 400 = 160,000

10. 67.5 Joules | Ec = 1/2 * m * v2 | Ec = 1/2 * 15 * (3)(3) | Ec = 1/2 * 15 * 9 = 67.5

4. The Editors of Encyclopaedia Britannica. (2025b, marzo 27). Energy | Definition, Types, Examples, & Facts. Encyclopedia Britannica. https://www.britannica.com/science/energy

5. Energy - BBC Bitesize. (2023, 1 marzo). BBC Bitesize. https://www.bbc.co.uk/bitesize/articles/zmxrbqt#zcnhtrd