A 12 mm thick plate is connected to two 8 mm plates, on either side through a 16 mm diameter power driven field rivet as shown in the figure below. Assuming permissible shear stress as 90MPa and permissible bearing stress as 270 MPa in the rivet, the rivet value of the joint is

Consider the following statements for a compression member

$${\rm I}.\,\,\,\,$$ The elastic critical stress in compression increases with decrease in slenderness ratio

$${\rm II}.\,\,\,\,$$ The effective length depends on the boundary conditions at its ends

$${\rm III}.\,\,\,\,$$ The elastic critical stress in compression is independent of the slenderness ratio

$${\rm IV}.\,\,\,\,$$ The ratio of the effective length to its radius of gyration is called as slenderness ratio

The TRUE statements are

The square root of the ratio of moment of inertia of the cross-section to its cross-sectional area is called

Consider the following statements:
$$1.$$ On a principal plane, only normal stress acts
$$2.$$ On a principal plane, both normal and shear stresses act
$$3.$$ On a principal plane, only shear stress acts
$$4.$$ Isotropic state of stress is independent of frame of reference.

Which of the above statements is/are correct ?