The air in a room has a mass of 50 kg and a specific heat of 1,000 J/(kg.°C). What is the change in thermal energy of the air when it warms from 20°C to 30°C?

Asolid round steel rod 6.25 mm in diameter and 375 mm long is rigidly bonded to the end of solid square brass rod 25 mm on a side and 300 mm long. the geometric axes of the bare are along the same line. an axial tensile force of 5.4 kn is applied at the extreme ends of the assembly. for steel e = 200 gpa and for brass e = 90 gpa. determine the total elongation for the assembly.