What point of a wave has negative amplitude? crest, wavelength, equilibrium, or trough

In a good thermo flask the main cause of heat loss is

When the displacement of a mass on a spring is 12a the half of the amplitude, what fraction of the mechanical energy is kinetic energy? at what displacement, as a fraction of a, is the mechanical energy half kinetic and half potential?

Acalorimeter uses the principle that thermal energy flows from hotter material to colder material until both reach the same