The relationship between energy and speed is described by the principles of physics, particularly in the context of relativity and classical mechanics.
In classical mechanics, the relationship between energy and speed can be understood through the concept of kinetic energy. Kinetic energy is the energy possessed by an object due to its motion. According to classical mechanics, the kinetic energy of an object is proportional to the square of its speed. In other words, if the speed of an object doubles, its kinetic energy increases by a factor of four.
In the context of relativity, the relationship between energy and speed is more complex. In Einstein's theory of special relativity, the energy of an object is described by the famous equation E = mc², where E is the energy, m is the rest mass of the object, and c is the speed of light.
According to this equation, the energy of an object is directly proportional to its mass. When an object is at rest (not moving), its energy is solely determined by its rest mass. However, as an object's speed increases, its energy also increases. The increase in energy is due to the relativistic effects of motion, including time dilation and relativistic mass.
Importantly, the rest mass of an object does not change with its speed. Instead, as an object approaches the speed of light, its relativistic mass increases, which contributes to the overall energy of the object. However, this increase in relativistic mass does not affect the rest mass of the object, which remains constant.
In summary, adding energy to an object increases its speed because energy is directly related to the object's mass and motion. The increase in speed is a result of the relationship between energy and kinetic energy, as described by classical mechanics, and the effects of relativistic mass in the context of special relativity.