#### Strenght of Materials

11

When a body is subjected to a direct tensile stress (sigma_x)n one plane accompanied by a simple shear stress (tau_(xy)), the maximum normal stress is

A. (sigma x)/(2) + 1/2 sqrt(sigma_x^2 + 4 tau_(xy)^2)
B. (sigma x)/(2) -1/2 sqrt(sigma_x^2 + 4 tau_(xy)^2)
C. (sigma x)/(2) + 1/2 sqrt(sigma_x^2 - 4 tau_(xy)^2)
D.  1/2 sqrt(sigma_x^2 + 4 tau_(xy)^2)

12
When a closely-coiled helical spring of mean diameter (D) is subjected to an axial load (W), the stiffness of the spring is given by
A. (Cd^4)/(D^3 n)
B. (Cd^4)/(2D^3 n)
C. (Cd^4)/(4D^3 n)
D. (Cd^4)/(8D^3 n)

13

The relation between modulus of elasticity (E) and modulus of rigidity (C) is given by

A. C = (mE)/(2(m+1))
B. C =(2(m+1))/(mE)
C. C = (2mE)/(m+1)
D. C =(m+1)/(mE)

14

The pull required to shear off a rivet, in double shear, per pitch length is

A. pi // 4 xx d^2 xx sigma_t
B. pi // 4 xx d^2 xx tau
C. pi // 2 xx d^2 xx sigma_t
D. pi // 2 xx d^2 xx tau

15
According to Euler's column theory, the crippling load for a column of length (l) with one end fixed and the other end hinged, is

A. (n^2 EI)/(l^2)
B. (n^2 EI)/(4l^2)
C. (2n^2 EI)/(l^2)
D. (4n^2 EI)/(l^2)