The energy possessed by a body due to its position or change in shape is called:

Potential energy is the energy stored in an object because of its position, shape or configuration. It is called "potential" because it has the potential to do work when it is released.

There are two main types of mechanical potential energy:

Gravitational potential energy: the energy an object has because of its height above the ground (its position in a gravitational field). It is calculated as PE = mgh, where m is the mass of the object, g is the acceleration due to gravity (about 9.8 m/s²) and h is its height above a reference level. For example, water stored behind a dam, a book on a high shelf, or a raised hammer has gravitational potential energy.

Elastic potential energy: the energy stored in an object when it is stretched, compressed or twisted (its shape is changed). For example, a stretched rubber band, a wound-up spring in a toy car or a watch, a drawn bow and a compressed spring have elastic potential energy. For a spring, it is ½kx², where k is the spring constant and x is the extension.

Potential energy can be converted into kinetic energy and back again. For example:

When an object falls from a height, its potential energy decreases and its kinetic energy increases. Just before it hits the ground, almost all its potential energy has become kinetic energy (ignoring air resistance).

In a swinging pendulum, energy keeps changing between potential energy (maximum at the highest points) and kinetic energy (maximum at the lowest point).

In a hydroelectric power station, the potential energy of water stored at a height in a dam is converted into the kinetic energy of flowing water, which turns turbines to produce electricity.

When an arrow is released from a stretched bow, the elastic potential energy of the bow is converted into the kinetic energy of the arrow.

Throughout these changes, the total mechanical energy (PE + KE) remains constant if no energy is lost to friction or air resistance. This follows from the law of conservation of energy.

Other forms of stored energy include chemical energy (in fuels, food and batteries) and nuclear energy (in atomic nuclei).

Why not the other options?

• ✗Kinetic energy is the energy of motion (½mv²).
• ✗Thermal energy is the energy due to the random motion of particles (heat).
• ✗Chemical energy is stored in the bonds of chemical compounds.