A rigid bar ABC is supported by a pin at A and a 100 mm wide by 5 mm thick aluminum (E=70 GPa; a= 22.5 x 106/°C; v = 0.33) alloy bar at B. A strain gage affixed to the surface of the aluminum bar is used to measure its longitudinal strain. Before the load P is applied to the rigid bar at C, the strain gage measure zero longitudinal strain at ambient temperature of 20°C. After the load P is applied to the rigid bar at C and the temperature drops to -20°C, a longitudinal strain of 2,400 μs is measured in the aluminum bar. Determine: a) The stress in the aluminum bar (1). Hint: There are two strain here b) The magnitude of the load P. c) The change in the width of the aluminum bar (i.e. the 100 mm dimension) Hint: The Poisson ratio is related to mechanical load 1.3 m (1) B 1.5 m 100 mm Strain gage 1.0 m