# Gravity and Energy

Gravity is the force by which a body draws another body to its centre. Gravity keeps all the planets in orbit around the sun. In physics, energy is the potential to do work. Energy exists in two primary forms: potential energy and kinetic energy. Various physical processes cause energy to transform from kinetic to potential or the reverse. This article will explore the relationship between energy and gravity and how they affect and interact with each other.

## Relationship between Gravity and Energy

Gravitational potential energy, or gravitational energy, is an object’s potential energy with respect to another object due to gravity. It is converted into kinetic energy when the objects fall toward each other.

The following formula gives the relationship between energy and gravity:

U = mgh

U is the gravitational potential energy in kgm2/s2, m is the mass in kilograms, g is the acceleration due to gravity (9.8 m/s2 at the earth’s surface), and h is the height in metres.

### How does gravity affect potential energy?

Gravity causes objects at a significant height to fall to the ground. Suppose a body is placed at a certain height. The potential energy reserved in the body is responsible for making the body move downwards due to gravity. As the body falls to the ground, the potential energy transforms into kinetic energy. A body falling from a greater height obtains greater velocity. Hence, it is evident that gravity affects the potential energy inversely.

## Gravitational Potential Energy in Action

The transformation of potential energy to kinetic and vice versa can be observed in the pendulum. The gravitational potential energy is transformed into kinetic energy when the pendulum swings downwards. When the pendulum bob is at its most elevated point, there is no kinetic energy, but the gravitational potential energy is the greatest. At the bottom of the pendulum’s swing, the gravitational potential energy is at a minimum, and the kinetic energy is at its maximum. The bob’s swing will reduce with each swing because some energy is transferred as heat to the surroundings.

## Gravitational Potential Energy Examples

In this section, we will discuss some examples of gravitational potential energy.

### Water stored behind a dam

The gravitational potential energy is stored in the overhead tank due to the difference in the water height in the hydroelectric dam and the water on the opposite side. When the water flows from the overhead tank to the ground, the potential energy is transformed into kinetic energy, which rotates the turbine.

### A book on a shelf

A book on a shelf in the library has potential energy because if it is nudged off the shelf, then gravity will accelerate the book giving the book kinetic energy.

### A child on a swing

A child enjoying a to-and-fro motion on the swing develops gravitational potential energy due to its height from the ground.

### A bird on a tree branch

The bird sitting on a tree branch possesses gravitational potential energy.

### An apple hanging from a tree

An apple hanging from a tree has potential energy due to its raised position.

#### Devin Haney

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