Explain what the difference between statically determinate and statically indeterminate structures is, and explain what is the standard procedure for determining all reactions for these two types of systems.

Consider the structure depicted in Figure A1. The structure is made up of two cylindrical rods denoted by (1) and (2) joined at C and restrained by rigid supports at A and E. State whether the structure of Figure A1, constrained to maintain the same overall lengths between positions A and E before and after applications of the concentrated loads $P_1$ and $P_2$, is statically determinate or indeterminate, and justify your answer.

Explain which conditions can be used to determine the reactions at the rigid supports A and E.

The cross section diameter and Young's modulus of rod (1) are respectively $E_1 = 70\ \mathrm{GPa}$ and $d_1 = 40\ \mathrm{mm}$, and the corresponding parameters of rod (2) are respectively $E_2 = 200\ \mathrm{GPa}$ and $d_2 = 30\ \mathrm{mm}$. The values of the axial loads $P_1$ and $P_2$ indicated in Figure A.1 are $P_1 = 90\ \mathrm{kN}$ and $P_2 = 120\ \mathrm{kN}$, and all four lengths indicated in the figure are in millimetres. Determine the reactions at the rigid supports A and E, providing their magnitude and orientation (left or right).

Determine the magnitude and direction (left or right) of the displacement of point c.