As shown in the figure bottom face of the sample is held rigidly bound and a shearing/tangential force F is applied on upper face of area A. The modulus of rigidity G is defined as the ratio of shear stress to the shear strain.
Shear stress=F/A and
shear strain =tan theta=(Deltax)/l
Delta x is the transverse displacement of the area on which force is acting and l is the initial length of the side.
G -= "Shear stress"/"Shear strain"= (F / A)/ ((Δ x) / l)
=>G= (F l)/( A Δ x)" Pa"
Inserting given values in SI units we get
G= 10 xx(10/100)/( 0.05/100)
=>G= 10 xx(10)/( 0.05)
=>G=2.0xx10^3" Pa"