Abstract

The energy dissipated by frictional forces in a tuning-fork was studied by means of two electrically-driven tuning-forks: (1) an ordinary fork, (2) a fork made by clamping two steel bars with a rectangular block between them, in a vise so that very little energy was expended in moving the stand upon which the fork was mounted. The following properties were investigated: (1) the equivalent length of a rigid straight bar turning through the same angle as the tangent at the end of the prongs; (2) the relation between the current driving a fork and the deflections of the prongs produced, both for steady and resonant deflections; (3) the logarithmic decrement, and the effect on the logarithmic decrement of damping due to vanes at the ends of the prongs; (4) the energy due to emission of sound. It was found that: (1) a straight bar about 73% of the whole length of the prong was approximately equal to the equivalent length; (2) the deflections of the prongs were proportional to the square of the current; (3) the change in the logarithmic decrement was roughly proportional to the area of the vanes; (4) about 3.5% of the total energy was converted into sound.

© 1928 Optical Society of America

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