﻿34 Dr. Dorothy Wrinch on the 



o£ magnitude T±dpdz — and these are equivalent, in the 

 usual way, to a radial force towards the centre of magnitude 



Tidpdsds/p, 



where ds~pd0; (2) of radial tensions 



T 2 ds dz and T 2 ds dz + dp d(T 2 ds dz)jdp, 

 towards and away from the centre, which together give a 

 £ ° rCe dpd0dzd( P T 2 )/dp 



away from the centre ; and (3) of longitudinal tensions each 



Fig.l. 



s p Ut 2 6s) 



T,t p/ .6s. 



of magnitude T s dp ds, in opposite directions. The resultant 

 force then is simply 



dp dz ds (d(pT 2 )jdr — Tj) 



away from the axis, and perpendicular to the axis of the 

 cylinder. The acceleration of the element is poo 2 towards 

 the centre and its mass is ardrdO, since we may, of course, 

 treat the density as constant over the element of volume. 

 We therefore have the equation of motion, 



d(pT 2 )/dp — T 1 = — arpar dr/dp. 



