7.4: Kinetic Energy
Kinetic energy is the ability of an object in motion to do work or enact change. It can take on many forms. For instance, water flowing down a waterfall has kinetic energy. In biological systems, particles of light travel and are absorbed by plants to create chemical energy. Animals consume the chemical energy and give off molecules that carry their scent through the air. They also generate kinetic energy when they run away from predators. Entire systems also possess kinetic energy, like the solar system, where the movement of entire planets and stars takes place.
Kinetic energy is the energy of objects in motion. For example, while water behind a dam has potential energy, water rapidly flowing down a waterfall has kinetic energy. If at the bottom of the waterfall, the water stopped moving and pooled, its energy would again be converted to potential energy.
In biological systems, kinetic energy takes on various forms as objects move in different ways. For example, particles of light—photons, that plants absorb to grow and make food, move very rapidly, change form, and are harnessed to do work—they’re used to make chemical energy in the form of carbohydrates.
Kinetic energy allows molecules that carry the scent of animals to drift away and attract a nearby predator. The chemical energy from the plants, when consumed by animals, allows the animals to run away from a predator—also a form of kinetic energy.
Kinetic energy can also be passed along from one object to another. For example, a person playing pool can hit a cue ball and its kinetic energy then hits another ball and puts it in motion. Entire systems can also possess kinetic energy—the movement of all the planets and stars in our solar system is kinetic energy.