Dyne

DYNE, the absolute unit of force (see Absolute system of units), equal to the force that imparts to a mass of one gram an acceleration equal to one absolute unit of acceleration (1 cm/sec.²), i.e., that changes the velocity of a mass of one gram by one centimeter in one second. To form an idea of the magnitude of a dyne, one can proceed as follows: it is known that a mass of one gram, attracted by the earth with a force of one gram, falls to the earth with an acceleration equal to the acceleration of gravity, i.e., approximately 980 cm/sec. Since, according to Newton's second law, the forces acting on the same mass are proportional to the accelerations they produce, the ratio of the dyne to the weight of one gram must equal the ratio of the accelerations they produce. This ratio is ¹/₉₈₀. Thus the dyne equals ¹/₉₈₀ of a gram, i.e., approximately one milligram. The dyne is the absolute measure of force, and if force F is measured in dynes, mass m on which the force acts in grams, and acceleration a in centimeters per second, then the relationship between these quantities will be expressed by the formula: F=ma. If the quantities F, m, and a are not expressed in absolute units, then in addition to F, m, and a, a factor K will enter into the expression, and the formula will transform as follows: F=Kma (1). If force is expressed in grams, mass in grams of mass, and acceleration in centimeters per second, then formula (1) takes the following form: F = ¹/₉₈₀ ma. In this case, when a unit of force (F = 1 gram of force) acts on a unit of mass (m = 1 gram of mass), a = 980.