Home - Machines Theory - Understanding gravitational energy

# Understanding gravitational energy

Gravitational energy is the energy associated with gravity as you may think. Gravity is a force that pulls two objects toward each other. What keeps you to the ground is the earth’s gravity and it causes objects to fall. It is the potential energy stored by an object because of its higher position compared to a lower position. Today you’ll get to know the definition and examples of gravitational energy in their various applications. You’ll also learn about gravity, potential energy, and newton’s law of gravitation.

## What is gravity?

Just as earlier mentioned, gravity is the force that pulls two objects toward each other. A good example of gravity is what keeps me and you on the ground, which is earth’s gravity. The gravity of the earth holds almost everything on this planet including trees, water, animals, buildings, and also the air we breathe is held by gravity. Furthermore, planets, moons, and stars in the universe have gravity. Even our own bodies have gravity but earth’s gravity is so strong that we can’t even notice.

## What is gravitational energy?

Gravitational energy is also known as gravitational potential energy is the potential energy a massive object has in relation to another massive object due to gravity. It is the potential energy associated with the gravitational field, which occurs when the objects fall towards each other. The energy increases when the two objects are brought further apart.

Potential energy is the energy an object has due to its position (in a gravitational or electric field) or its condition (as a stretched or compressed spring, as a chemical reactant, or by having rest mass).

Newton’s law of gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

## Examples of gravitational energy

A good example of gravitational energy is a pendulum that transfers gravitational potential energy to kinetic energy in a repetitive way. In the process, there is no kinetic energy when the ball is at the highest point of the swing, but its gravitational potential energy is at a maximum. Also, as the bob swings downward, gravitational potential energy is transferred to kinetic energy, and the bob accelerates.

Therefore, at the bottom of the swing, the bob’s kinetic energy is at a maximum and its gravitational potential energy is at a minimum. As the bob swings upward, its kinetic energy is transferred to gravitational potential energy again. The bob’s swing will become lower at each swing because some energy is transferred as heat to the surroundings.

Another good example is a book placed on top of a table. As the book is raised from the floor to the table, there is some external force that works against the gravitational force. If the book falls back to the floor, the “falling” energy the book receives is provided by the gravitational force. Thus, if the book falls off the table, this potential energy goes to accelerates the mass of the book and is converted into kinetic energy. When the book hits the floor, this kinetic energy is converted into heat and sound by the impact.

The factors that affect an object’s gravitational potential energy are its height relative to some reference point, its mass, and the strength of the gravitational field it is in. Thus, a book lying on a table has less gravitational potential energy than the same book on top of a taller cupboard and less gravitational potential energy than a heavier book lying on the same table.

An object at a certain height above the Moon’s surface has less gravitational potential energy than at the same height above the Earth’s surface because the Moon’s gravity is weaker. Note that “height” in the common sense of the term cannot be used for gravitational potential energy calculations when gravity is not assumed to be a constant.

Further examples of gravitational energy are water stored in a dam, roller coasters, a large boulder at the edge of a cliff, a skateboard on the top of a ramp.    