PHYSICS · Single correct · AP · Physics 2: Algebra-based · Thermodynamics · Thermodynamics
Problem
Two identical 2kg blocks, A and B, made of the same material are initially at 100∘C and 0∘C, respectively. All external surfaces of each block are covered with an ideal thermal insulator except for a small 2cm2 patch where the blocks are pressed together. The combined system is perfectly isolated from its surroundings. Which statement best describes the state of the system after a very long time has passed?
(a) Both blocks eventually reach the same temperature of 50∘C, and the net energy flow between them becomes zero.
(b) Block A remains warmer than Block B because the small contact area limits the amount of heat that can be transferred.
(c) Although both blocks settle at a common temperature of 50∘C, heat continues to flow from the former hot block to the former cold block because conduction is always present.
(d) Block B eventually becomes warmer than Block A because its lower initial temperature allows it to absorb heat more efficiently, causing an overshoot past equilibrium.