Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Kinetic Energy

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Kinetic Energy, energy possessed by an object, resulting from the motion of that object. The magnitude of the kinetic energy depends on both the mass and the speed of the object according to the equation

where m is the mass of the object and v2 is its speed multiplied by itself. The value of E can also be derived from the equation

E = (ma)d

where a is the acceleration applied to the mass, m, and d is the distance through which a acts. The relationships between kinetic and potential energy and among the concepts of force, distance, acceleration, and energy can be illustrated by the lifting and dropping of an object.

When the object is lifted from a surface a vertical force is applied to the object. As this force acts through a distance, energy is transferred to the object. The energy associated with an object held above a surface is termed potential energy. If the object is dropped, the potential energy is converted to kinetic energy. See Mechanics.