Two parallel and opposite forces, each of magnitude 4000 N, are applied tangentially to the upper and lower faces of a cubical metal block 25 cm on a side. Find the displacement of the upper surface relative to the lower surface (in x 10-5 cm ). The shear modulus for the metal is 80 Gpa.

We use the approximate from S=F/(Aϕ)Putting S=8×1010N/m2,F=4000N and A=(0.25m)2=6.25×10−2m2 in the above equation and solving for ϕ, we getϕ=(4000N)6.25×10−2m28×1010N/m2=8.0×10−7radThe displacement of the upper surface is given by d=Lϕ,where L is an edge of the cube.∴ d=8.0×10−7(25cm)=2.0×10−5cm