A rod of steel is 20 m long at a temperature of 200C. find the free expansion of the rod when the temperature is raised to 650C. Find the temperature stress produced : (i) when the expansion of the rod is prevented (ii) when the rod is permitted to expand by 5.8 mm. Take a=12×10-6 per 0 C (coefficient of thermal expansion) and E=2×105 N/mm2.