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    				| 1. | Calculate the torque N twisting a steel tube of length `l=3.0m` through an angle `varphi=2.0^@` about its axis, if the inside and outside diameters of the tube are equal to `d_1=30mm` and `d_2=50mm`. | 
| Answer» Clearly `N=underset(d_1//2)overset(d_z//2)int(2pir^3drvarphiG)/(l)=(pi)/(32l)Gvarphi(d_2^4-d_1^4)` using `G=81GPa=8*1xx10^(10)N/m^2` `d_2=5xx10^-2m, d_1=3xx10^-2m` `varphi=2*0^@=(pi)/(90)` radius, `l=3m` `N=(pixx8*1xxpi)/(32xx3xx90)(625-81)xx10^2N*m` `=0*5033xx10^3N*m~~0*5k N*m` | |