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potential energyThe energy possessed by a body or system by virtue of its position or configuration. It is equal to the work done by the system changing from its given state to some standard state. In a gravitational field, a mass m placed at a height h above a standard level (say the surface of the Earth) has potential energy mgh, where g is the acceleration of gravity.
the part of the total mechanical energy of a system that depends on the relative positions of the particles making up the system and on the positions of the particles in the external force field, such as a gravitational field. The potential energy of a system in a given position is numerically equal to the work that the forces acting on the system perform when the system is shifted from this position to a position in which the potential energy is arbitrarily assumed to be equal to zero.
It follows from this definition that the concept of potential energy holds only for conservative systems, that is, systems in which the work of the acting forces depends only on the initial and final positions of the system. Thus, for a weight P raised to a height h, the potential energy will be equal to Ph; it will be equal to zero when h equals zero. For a weight attached to a spring, the potential energy will be 0.5cλ2, where λ is the elongation or compression of the spring and c is the spring’s stiffness. Again, the energy is zero when λ is zero. For two particles with masses m1 and m2, attracted according to the law of universal gravitation, the potential energy is —fm1m2/r, where f is the gravitational constant and r is the distance between the particles. In this case, the energy is zero when r = ∞. The potential energy of two point charges e1 and e2 is calculated in a similar manner.
S. M. TARG