# What is the Law of Conservation of Energy?

Energy cannot be destroyed, but it can be transformed, as when solar panels convert light and radiation from the sun into usable electrical energy.

The law of conservation of energy is a principle of physics that states that, in a closed system, energy cannot be created or destroyed. It is expressed in the First Law of Thermodynamics, which states that energy can be transformed into many forms, such as light or heat, but the sum total of energies is conserved or remains constant. Usually, this law is illustrated with a pendulum. The height at which the ball is dropped at one end of the pendulum will be equal to the height at which the ball will reach at the other end. In fact, in a theoretically frictionless environment, the ball will continue to swing back and forth forever.

An example of potential energy is a ball on top of a hill.

As a fundamental concept in physics, the law of conservation of energy provides an explanation of how energy is conserved and converted within a system. Generally, one form of energy can be converted into another form of energy. For example, potential energy can be converted to kinetic energy.

The kinetic energy of a specific object is the energy it has while it is in motion. As an expression, the kinetic energy is equal to half the object’s mass multiplied by the square of the object’s velocity, or KE = 1 / 2mv 2 . Kinetic energy consists of three types of energies. Vibrational kinetic energy is energy due to vibrational motion and rotational kinetic energy is energy due to rotational motion. Translational kinetic energy is the energy due to the movement of the center of mass from one point to another.