Howl's Moving Castle

Howl's Moving Castle is a famous Japanese film directed by Hayao Miyazaki (who also directed Spirited Away). This mural depicts the magic moving castle, and also has some physics equations hidden in it:

delta U = U final - U initial = Q-W, where U is internal energy, W is work done by the system, and Q is heat added to the system.

ec (efficiency of a carnot engine, which is an ideal heat engine with maximum efficiency) = (Th-Tc)/Th = 1- Tc/Th, where Th is the temperature of the hot reservoir and Tc is the temperature of the cold reservoir.

e (efficiency of any heat engine) = W/Qh = (Qh-Qc)/Qh = 1 - Qc/Qh, where W is work, Qh is the heat input from the hot reservoir, and Qc is the heat output into the cold reservoir (e is always less than 1).