What is the Difference between Potential and Kinetic Energy?

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Chart of energy vs position

Energy is a quantity that is often understood as the ability a physical system has to do work on other physical systems. Since work is defined as force acting through a distance, energy is always equivalent to the ability to exert pulls or pushes against the basic forces of nature, along a path of certain length. The total energy contained in an object is identified with its mass, energy (like mass), cannot be created or destroyed. In the International System of Units (SI), energy is measured in ‘joules’. Energy, like mass is a scalar physical quantity. This Energy takes many forms such as Potential energy, Kinetic energy, Electromagnetic energy, Thermal energy, Chemical energy etc. All energy is basically categorized into 2 classes known as the Kinetic energy and Potential energy.


What is Potential Energy?

Potential energy is stored energy. The word potential to define energy was coined by Scottish physicist William Rankine in 19th century. It is the energy that exists within an object. It is the stored energy of position possessed by an object. In other words, potential energy is the energy an object possesses or displays by virtue of its state of rest. Potential energy is also known as ‘restoring energy’ as it tends to force an object to return to its original state of rest. The following are the potential forms of energy. The formula for calculating Potential energy is P.E. = m * g * h, where 'm' is the mass of an object, 'g' is the acceleration of gravity, 'h' is the height of the object.

  • Stored mechanical energy: The energy which is possessed by an object due to its stored energy of position. E.g., rubber bands, springs
  • Nuclear energy: Energy locked in the nucleus of the atom
  • Chemical energy: The energy stored in food, wood, coal, petroleum and other fuels
  • Gravitational energy: Energy stored as a result of gravitational forces concentrated by the earth for the object. E.g., The water held back by a dam.


What is Kinetic energy?

Kinetic energy is the energy of motion. The word kinetic came from the Greek word “kinesis” meaning motion. It is the energy an object displays or possesses because of some kind of motion or action. Kinetic energy can also be passed from one moving object to another when a collision or contact takes place. This does not happen in potential energy. The kinetic energy of a body with the mass ‘m’ moving at a velocity ‘v’ is one half the products of the mass of the body and the square of its velocity. i.e., K.E. = (1/2) * m * v2. The average kinetic energy of the atoms or molecules is measured by the temperature of the body. The following are the types of kinetic energy.

  • Electricity: Energy produced when something upsets the balancing force between electrons and proton in atoms
  •  Light or Radiant energy: Waves that emit energy. E.g. gamma rays, x-rays
  •  Heat or Thermal energy: Created by heat. The hotter an object gets the more thermal energy it possesses


What is the basic difference between potential and kinetic energy?

  • The difference between kinetic and potential energy all comes down to a very simple property of the object. If an object is moving, then it has kinetic energy. Potential energy is the stored energy in an object which can be released under right conditions. So, the difference between both of them comes down to whether an object is moving or not
  • While potential energy is non-related to the environment of the object, kinetic energy is completely relative to the other moving or stationary objects in the environment
  • The difference between both the energies and the conversion of one another is explained by the falling of rock from a cliff, when its energy of position is changed to energy of motion
  • If we consider a swing, as the suspended body moves upward in its swing, its kinetic energy is continuously being changed into potential energy: the higher it goes the greater becomes the energy that it owes to its position. At the top of the swing the change from kinetic to potential energy is complete, and in the course of the downward motion that follows the potential energy is in turn converted to kinetic energy
  • A water fall has both potential and kinetic energies by virtue of its height and by the movement of the water. When the water is at the top of a water fall, it is full of potential energy. But when the water touches the bottom, it has only kinetic energy and no potential energy.


What is the conclusion?

According to the law of conservation of energy, energy can neither be created nor be destroyed. So, the conversion of energy from kinetic to potential and vice versa is the basis of the functioning of the universe. In other words, potential and kinetic energy are the same.

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