Question

What are mechanical equilibrium and thermal equilibrium?

Hint:

Mechanical equilibrium involves forces and torques; thermal equilibrium involves temperature uniformity.

Answer 1

Mechanical Equilibrium: A system is in mechanical equilibrium when the net force and net torque on it are zero, resulting in no acceleration or rotation (e.g., a book at rest on a table).
Thermal Equilibrium: A system is in thermal equilibrium when there is no net heat flow between its parts or with its surroundings, implying all parts are at the same temperature (e.g., two objects in contact reaching the same temperature).
Answer: Mechanical equilibrium: zero net force and torque; thermal equilibrium: no net heat flow, uniform temperature.