Two identical aluminum disks, A and B, are initially at different uniform temperatures. At clock time t=0, the disks are placed in direct thermal contact and immediately insulated from the surroundings. Ten minutes later two identical laboratory thermometers are gently pressed against the center of each disk and allowed to stabilize. The thermometers register
• Disk A: 25.3∘C,
• Disk B: 25.0∘C.
Each thermometer has a stated reading uncertainty of ±0.5∘C.
Assume the thermometers themselves absorb negligible energy from the disks.
(a) Determine, within the stated measurement uncertainty, whether the two disks can be considered to have reached thermal equilibrium at the moment of the reading. Clearly state the reasoning that leads to your conclusion.
(b) On a microscopic level, collisions between atoms in the region of contact lead to the approach toward equilibrium. Describe qualitatively how the distribution of molecular kinetic energies changes from t=0 to ten minutes later to account for the macroscopic temperature readings.
(c) Propose one additional experimental observation—other than taking another thermometer reading—that would provide evidence about whether net energy transfer between the disks is still occurring. Explain how the observation would support or refute the presence of thermal equilibrium.