Evolutions of the collapsing systems as a function of central density and time using EOS A (black), EOS B (magenta), and EOS C (grey). a), b) Normalised force differential ΔF between total pressure F_pres, gravity F_grav, and ram pressure F_ram (integrated over the volume of the first core) as a function of central density. The green dotted ΔF = 0 line represents hydrostatic equilibrium. c) The separate force components from gravity F_grav (solid), gas pressure F_gas (dashed), radiation pressure F_rad (dotted), and ram pressure F_ram (dot-dash) as a function of central density. d) Central density as a function of time. e) Central temperature as a function of central density. f) Central temperature as a function of time. g) Adiabatic index along the thermal tracks from panel e). h) Adiabatic index at the centre of the grid as a function of time. The time of first core formation t₀ is assumed to be when the central density reaches 10^-13 g cm^-3. In all panels, two thermal bounces are labelled ① and ② (see text).