Pressure and pressure differences in fluids (physics only)

The key evidence to use is that Pressure and pressure differences in fluids (physics only) sits inside 4.5 Forces and should be revised as a connected set of physical ideas, not as isolated definitions. Context: the topic brings together Pressure on a surface (physics only), Pressure in liquids (physics only), Atmospheric pressure (physics only) and asks students to move between description, calculation, graph interpretation and explanation where appropriate. Key Concept: identify the quantity, model or interaction first, then state how evidence or a mathematical relationship supports it. Worked Example: for a typical exam item, name the relevant principle, use the given data or diagram, and finish with a sentence that interprets the physical consequence. Exam Focus: keep command words visible; describe asks for features, explain asks for a causal link, calculate requires equation, substitution and unit, and evaluate needs evidence. Common Mistake: avoid using a nearby concept as a substitute, such as confusing field with force, current with potential difference, speed with acceleration, or red-shift evidence with the Big Bang model itself.