﻿Motion of a Sphere in a Viscous Fluid. 



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The general arrangement of the apparatus is shown in 

 tig. 1. The trough T was placed on a table fixed to the 

 wall of the room. Above it was a long frame AB resting 

 •on the rollers RR, and the sphere S was attached to a piece 



Fig. 1. 



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Arrangement of apparatus 



of steel wire fixed to the middle of the frame, so that the 

 latter in moving along on the rollers carried the sphere from 

 one end of the trough to the other. The position of the 

 sphere was adjusted so that its centre moved along the centre 

 line of the trough. Motion is given to the frame by means 

 ■of a heavy bar, BD, hinged to it and resting on the axle 

 of the pulley F, which is connected by a set of reduction- 

 pulleys to the axle of a small electric motor, M. The 

 velocity of the frame can be varied by varying the resistance 

 in the armature circuit of the motor and also, if necessary, by 

 varying the reduction ratio of the connecting pulleys. The 

 motor was kept continually running and the frame started by 

 •dropping the bar on the axle. The frame being very light it 

 immediately took up the velocity of the axle, and thus the 

 sphere moved along the trough with a uniform velocity. 



The motion of the liquid is rendered visible by mixing 

 up a little aluminium powder with a drop of glycerine and 

 stirring it into the liquid in the trough. The little aluminium 

 flakes remain suspended in the water for several hours, and 

 when illuminated by a beam of light from an arc lamp show 

 clearly the motion of the liquid surrounding the moving- 

 sphere. 



A camera was arranged in front of the trough, and when 

 the motion is photographed the aluminium particles trace out 

 curves on the plates which serve to measure the velocity of 

 the fluid and enable the stream-lines to be plotted out. 



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