A 0.05 m cube has its upper face displaced by 0.2 cm by a tangential force of 8 N. Calculate the modulus of rigidity in×104Nm−2 of the material of the cube.

l=5×10−2m,Δl=0.2cm=0.2×10−2m,F=8N Shearing strain =Δll=0.25=0.04 Shearing stress =Fl×l=85×10−22=3200Nm−2η= Shearing stress Shearing strain=32000.04=80000Nm−2=8×104Nm−2