Conservation of Energy

Mechanical Energy

In science, mechanical energy is the sum of potential energy and kinetic energy. It is the energy associated with the motion and position of an object. The law of conservation of mechanical energy states that in an isolated system that is only subject to conservative forces the mechanical energy is constant.

Types of Mechanical Energy:

Potential and Kinetic energy


Potential Energy

In physics, potential energy is the energy of an object or a system due to the position of the body or the arrangement of the particles of the system. The SI unit for measuring work and energy is the joule (symbol J).

Formula of Potential energy






Examples

Case 1: A cat had climbed at the top of the tree. The Tree is 20 meters high and the cat weighs 6kg. How much potential energy does the cat have?
 m = 6 kg, h = 20 m, g = 9.8 m/s²(Gravitational Acceleration of the earth)
  Step 1: Substitute the values in the below potential energy formula:
            Potential Energy: PE = m x g x h
            = 6 x 9.8 x 20
            Potential Energy: PE = 1176 Joules 



Kinetic Energy

In physics, the kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity.

Formula of Kinetic energy

Examples

Case 1: Determine the Kinetic energy of a 500kg roller coaster train which moves at a speed of 20 m/s.
 M = 500 kg, V = 20 m/s
  Step 1: Substitute the values in the below kinectic energy formula:
            Kinetic Energy: E_k = ½ mv²
            = ½ x 500 x 20²
            = 0.5 x 500 x 400
            Kinetic Energy: E_k = 100000 Joules or 1 x 10⁵ Joules



What is conservation of energy

The law of conservation of energy, first formulated in the nineteenth century, is a law of physics. It states that the total amount of energy in isolated system remains constant over time. The total energy is said to be conserved over time. For an isolated system, this law means that energy can change its location within the system, and that it can change form within the system, for instance chemical energy can become kinetic energy, but that energy can be neither created nor destroyed.

Examples of conservation of energy

To scientists, conservation of energy is not saving energy. The law of conservation of energy says that energy is neither created nor destroyed. When we use energy, it doesn’t disappear. We change it from one form of energy into another. A car engine burns gasoline, converting the chemical energy in gasoline into mechanical energy. Solar cells change radiant energy into electrical energy. Energy changes form, but the total amount of energy in the universe stays the same. Scientists at the Department of Energy think they have discovered a mysterious new form of energy called "dark energy" that is actually causing the universe to grow!