$7\mathrm{.}14$ P$7\mathrm{.}14($concentric cylinder device$)...$

$=f(,,K,D_1,D_2,l)$

$KFL.=0\mathrm{.}5N*\frac{s}{m^2},K=14N*m,l=0\mathrm{.}3m{D}_1{D}_2.,,.$

$$: $,.=0=0.$

$\backslash$table$[[(rad),(ra\frac{d}{s})$