Final answer:
The incompressibility of liquids causes a wine bottle to break when a cork is pounded directly against it; air cushions the impact and prevents breakage.
Step-by-step explanation:
A wine bottle can break when a cork is pounded directly against the liquid because liquids are incompressible, and hitting the cork transmits the force directly to the glass without absorption, resulting in high pressure and potential breakage. Conversely, if there is air between the cork and the liquid, the air acts as a cushion, absorbing the force from the cork and reducing the pressure on the glass, preventing the bottle from breaking. This scenario demonstrates the physical properties of liquids, such as incompressibility, and the cushioning effect of gases, like air.