Mechanical energy

In physical science, mechanical energy is the total energy an object has because of its position and movement. It has two main parts: potential energy, which comes from where the object is, and kinetic energy, which comes from how fast the object is moving.

One important rule is that in some situations, mechanical energy stays the same. This means if an object moves against a force, its potential energy goes up, and if its speed changes, its kinetic energy changes too. But in real life, forces like friction can make mechanical energy change a little.

Mechanical energy can turn into other kinds of energy. For example, an electric motor changes electrical energy into mechanical energy, an electric generator changes mechanical energy into electrical energy, and a heat engine turns heat into mechanical energy. James Prescott Joule showed that losing mechanical energy can make the temperature rise.

General

Energy helps us understand how things work. Mechanical energy is the total of two types of energy in an object: potential energy and kinetic energy.

Potential energy is stored energy that depends on where an object is. For example, if you lift a book higher, it gains more potential energy because of gravity. Kinetic energy is the energy of motion. When something moves faster, it has more kinetic energy.

The rule of conservation of mechanical energy tells us that if only certain kinds of forces are acting on an object, its total mechanical energy stays the same.

Conservation of mechanical energy

Main article: Pendulum

Main article: Irreversible process

Main article: Vis-viva equation

Mechanical energy is the total energy an object has from moving and its position. This includes kinetic energy from motion and potential energy from position.

When an object moves without outside forces like friction, its mechanical energy stays the same. For example, a swinging pendulum moves back and forth, changing between kinetic and potential energy but keeping the total the same. In real life, small forces like air can change this a little, but the idea still helps us understand many situations.

Conversion

Many machines can change mechanical energy into other types of energy and back again. For example, an electric motor turns electrical energy into mechanical energy, while a generator does the opposite, turning mechanical energy into electricity. A hydroelectric powerplant uses the movement of water to create electricity. An internal combustion engine gets mechanical energy by burning fuel, and often uses that energy to make electricity. A steam engine uses the energy from steam to create motion, and a turbine changes the movement of liquids or gases into mechanical energy.

Distinction from other types

Energy can be grouped into different types based on the areas of science that study them.

• Chemical energy is a kind of stored energy found in chemical bonds and is studied in chemistry.
• Nuclear energy is energy stored in the interactions between particles in the atomic nucleus and is studied in nuclear physics.
• Electromagnetic energy involves electric charges, magnetic fields, and photons. It is studied in electromagnetism.
• Quantum mechanics looks at different forms of energy, such as the energy levels of electrons in an atom.