Mathematical points endowed with inertia coefficients, separated by finite intervals, and acting on one another with forces in the lines joining them subject to the law of equality of action and reaction.

It is usually accurate enough in deflection calculations to take for I the moment of inertia at the centre of the beam and to consider it constant for the length of the beam.

Single needles are never used, two being the least number, and these so arranged that the moment of inertia about every diameter of the card shall be the same.

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When the atoms are in motion these strain-forms produce straining and unstraining in the aether as they pass across it, which in its motional or kinetic aspect constitutes the resulting magnetic field; as the strains are slight the coefficient of ultimate inertia here involved must be great.

Another type of quadratic moment is supplied by the deviationmoments, or products of inertia of a distribution of matter.

The new A, B, C are called the principal moments of inertia at 0.

On the other hand, under the influence of the mechanics of his day, which had hardly distinguished between inertia, or the inability of a body to change itself, and resistance or the ability of bodies to oppose one another, he concluded that, as inertia is passive, so is resistance, and refused to recognize that in collision the mutual resistance of moving bodies is a force, or active power, of changing their movements in opposite directions.

A, B, C are the moments of inertia about the co-ordinate axes, and F, G, H are the products of inertia with respect to the pairs of co-ordinate planes.

The graphical methods of determining the moment of inertia of a plane system of particles with respect to any line in its plane may be briefly noticed.

Prince Andrew had grown thinner, paler, and more manly- looking, but what amazed and estranged Pierre till he got used to it were his inertia and a wrinkle on his brow indicating prolonged concentration on some one thought.