Question

A glass wire of 1 mm diameter and length 2 m is used to suspend a mass of 2 kg from the ceiling. The mass is now subjected to a moment t about the vertical axis, causing the wire to be loaded in torsion as well as tension, and brittle failure is observed to occur when the mass has been rotated through an angle of 135o . What is the maximum mass that could be supported by a similar wire if loading were purely tensile (no rotation of the end)? (gglass = 35 gpa).

Answer 1

?solution
the mass of 2kg weight
W= 2× 9.81 = 19.62N
and will cause a tensile stress
= W/ A
=
$\frac{19.62}{\pi \times \frac{1 {}^{2} }{4} } = 24.95 n |mm {}^{2}$
torsion will produce a shear stress T, where
T/J = t/r =G trianglemax/L
=
$\frac{35 \times 10 {}^{3} \times 135 \times \frac{\pi}{180} \times 0.5 }{2000} = 20.62mpa$
glass is a brittle metarial which we assume fracture when the maximum
now see your answer