Letter | Published:

Air-drag and the Equilibrium of Whirling Threads

Naturevolume 140pages194195 (1937) | Download Citation



IN the absence of all resistance to motion and assuming perfect flexibility, the differential equations of motion for a thread which carries a small spherical 'bob' and is whirled rapidly about a vertical axis by a horizontal arm give us an approximate solution for small amplitudes a plane sine wave—with reference to moving axes—leading to the well-known formula for plane vibrations1. This approximate solution throws no light whatever on the stability of whirling threads as observed experimentally in air: these threads show 'necks' of appreciable amplitude in place of point nodes, the necks increasing in diameter the farther they are from the 'bob'. With sufficiently long threads and a large radius of the whirling arm, the sine outline disappears altogether.

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  1. 1

    Hall, H. W., NATURE, 138, 932 (Nov. 28, 1936).

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  1. Experimental Department, Fine Cotton Spinners' and Doublers' Association Ltd., Rock Bank, Bollington, Cheshire

    • E. R. GOSHAWK


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