What is Gravitational Potential Energy?
Gravitational potential energy is energy stored within an object due to its height above the surface of the Earth. In order for an object to be lifted vertically upwards, work must be done against the downward pull of gravity. The amount of energy used to lift the object against gravity is then stored as gravitational potential energy within the object. When the object is released and falls towards the Earth, the stored energy is converted into kinetic energy, the energy of movement.
The amount of gravitational potential energy that an object possesses depends on the object’s mass or weight, its height above the surface, and the strength of the field of gravity. A heavy object will have more gravitational potential energy than a lighter object. An object one mile up in the sky will have more energy than the same object one foot from the surface. In addition, an object lifted up on the Moon, which has a weaker field of gravity than the Earth, will have less potential energy than the same object at a similar height above the Earth.
The Earth’s gravitational force field varies in strength from location to location. This variation is, however, so small as to be almost negligible. In physics, therefore, the acceleration due to gravity near the surface of the Earth in usually considered a constant. This constant is stated in meters per second per second (m/s2), as follows: gravity = 9.8 m/s2.
A potential energy definition must account for the mass of an object, its height, and the force of the gravitational field. A simple potential energy formula for an object lifted up from the surface of the earth could therefore be stated as follows: potential energy = mass of object in kilograms x 9.8 x height of object in meters. This potential energy equation uses the constant value 9.8 to represent the force of acceleration generated by gravity on Earth.
There are many practical applications for the use of gravitational potential energy, such as the production of hydroelectricity. For example, a hydroelectric power plant may have an excess of electricity at times of low demand. This excess power may be used to pump water from a low reservoir to a higher reservoir. Doing so stores the power as gravitational potential energy. At times of peak demand, the water can be released from the high reservoir, and the potential energy that was stored can be used to generate more electricity.
Written by C. Martin
