Pressure

• Does Hydrostatic Pressure Act in Lateral Directions?
  In a fluid at rest, pressure is the same in every direction at a point; lateral force comes from the wall’s normal and varies with depth.
• How Does Pressure Affect the Expansion of the Universe?
  In cosmology, pressure contributes to gravity: positive pressure slows expansion, while sufficiently negative pressure can accelerate it.
• How to Derive a Thermodynamic Relation from Helmholtz Free Energy
  Starting from Helmholtz free energy, derive pressure and entropy identities and show why (∂U/∂V)T = T(∂P/∂T)V − P.
• How to Calculate Melting and Boiling Points at Different Pressures
  Use the Clausius–Clapeyron equation for boiling points and the Clapeyron equation for melting points, with a reference temperature and phase-change data.