The edge of an aluminium cube is 10 cm long. One face of the cube is firmly fixed to a vertical wall. A mass of 100 kg is then attached to the opposite face of the cube. The shear modulus of aluminium is 25 GPa. What is the vertical deflection of this face?
Given data,
Edge of the aluminium cube, L = 10 cm = 0.1 m
The mass attached to the cube, m = 100 kg.
Shear modulus (η) of aluminium = 25 GPa = 25× 109 Pa.
Shear modulus, η = Shear stress/ Shear strain = 
Where,
F = applied force = mg = 100kg × 9.8ms-2 = 980 N
A = Area of one of the faces of the cube = L2 = 0.1×0.1 = 0.01m2
ΔL = vertical deflection of the cube.
Modifying the formula of Shear modulus,
ΔL = 
Substituting all the values mentioned above, we get,
⇒ ΔL = 
⇒ ΔL = 3.92 × 10-7m
Hence, the vertical deflection of this face of the cube is
3.92× 10-7 m.