I don't understand how to solve these problems.

Please help me!!

A 1-D bar that is xed at one end and free at the other end is subjected to a body force given by 5(a) = 450 + 2.5.1; N/mm as shown in Fig. 3. Assume A = 600 mm2 and E = 200 GPa. Use 1D linear nite elements with the node and element numbers shown: (a) Write the global stiffness matrix. (b) Evaluate the body force vector for each element. (c) Assemble the local body force vectors into global force vector with reactions. (d) Apply boundary conditions and solve for the displacement of nodes 2 and 3. (c) Find the stress in each element. b(x) = 450 + 2.5x N/mm h .I- l- F' U"' 2 3 90 mm -h-|- 90 mm --|