The glass rod (g - glass) and the spring (s - spring) are firmly connected to each other. The rods are subjected to a thermal load (?T = T_U - T₀). The dimensions of the picture are given at the initial temperature T₀. The Young's modulus of the rod is E_g, the temperature coefficient of the length is ?_g, the length at the initial temperature is L_go and the cross-sectional area is A_g. The spring constant of the spring is k, the temperature coefficient of the length is ?_s and the length at the initial temperature is L_so.

Derive a symbolic expression for the normal force N acting on the rod and spring as a function of temperature change ?T. There is no normal force N(T₀) = 0 at the initial temperature.

Instructions: The same normal force (Newton III) acts on the rod and the spring. Like the spring constant, the thermal expansion coefficient of the spring length takes into account both the material of the spring and its shape.

Ag Lgo Olg Eg * L Lso