Three solid objects—A, B, and C—are made of the same material and have identical mass and specific heat capacity.
• Object A is initially at 120 °C.
• Object B is initially at 40 °C.
• Objects A and B are placed in thermal contact inside a perfectly insulated container and are allowed to reach equilibrium. Their common temperature is observed to be 80 °C.
• Object B is then removed and immediately placed in thermal contact with object C, which is initially at 10 °C, inside a second perfectly insulated container. After equilibrium is re-established, the common temperature of B and C is 45 °C.
Assume no energy is exchanged with the surroundings at any time.
(a) For each of the two interactions described, identify the direction of net energy transfer between the objects and relate that direction to their initial temperatures.
(b) Immediately after the second interaction ends, objects A and C are at 80 °C and 45 °C, respectively. If these two objects are now placed in thermal contact inside an insulated container, will they initially be in thermal equilibrium? Explain your reasoning using the definition of thermal equilibrium.
(c) Under the conditions stated above, calculate the final equilibrium temperature that objects A and C will reach when brought into contact. Justify your calculation.