QUESTION 5 5(a) A tube BC with rectangular cross-section is used to support a rigid body ABD as shown in Figure Q5. The tube BC is made of alloy with E= 80 GPa and yield = 120 MPa. The connections at A, B and C are pins. An external load P is applied downward at D. Find the maximum value of load P that can be applied for the support tube not to buckle. (8 marks) 80 mm 40 mm Cross-section of tube BC Rigid body ABD 2 m 50 mm 90 mm P B 2.5m 1.5 m D Figure Q5 C 5(b) If the load P is upward from the Q5(a), Find the maximum value of P that can be applied for the tube not to fail. (2 marks) QUESTION 4 The 10 kN load is applied at the free end of the bar as shown in Figure Q4. Let modulus of elasticity E = 200 GPa, the shear modulus G = 80 GPa, and the Poisson's ratio v=0.3. The diameter of the bar is 40 mm. a) Determine the displacement in -y direction of end D by using Castigliano's second theorem. (5 marks) b) Determine the rotation about x' axis of end D by using Castigliano's second theorem. (3 marks) c) Without any calculation, explain whether the rotation about x' axis of end D increases if the applied load is increased from 10 kN to 20 kN. (2 marks) Consider the strain energy due to axial, bending and torsion only. Neglect the strain energy due to transverse shear. 22 B 150 mm- Figure Q4 10 kN 200 mm 150 mm