AP Physics 1 / Topic
Fluids
Unit 8 covers fluids at rest and in motion: density and pressure, hydrostatic pressure with depth, Pascal's principle, buoyancy and Archimedes' principle, the continuity equation, and Bernoulli's equation.
What the exam asks
- Compute absolute and gauge pressure at depth in a fluid
- Apply Pascal's principle to hydraulic lifts
- Use Archimedes' principle for floating and submerged objects and apparent weight
- Apply the continuity equation to flow through changing pipe cross-sections
- Use Bernoulli's equation (and Torricelli's theorem) to relate pressure, speed, and height
Key formulas and rules
ρ = m/V; P = F/A
P = P0 + ρgh (depends on depth, not container shape)
F(b) = ρ(fluid)·V(displaced)·g; floating: F(b) = weight
A1v1 = A2v2 - narrower pipe, faster flow
P + ½ρv² + ρgh = constant; faster flow ⇒ lower pressure
efflux speed v = √(2gh)
Question bank breakdown
43
3
11 easy · 26 medium · 6 hard
Skills covered
Every question in the bank comes with a worked explanation, and most add a per-choice breakdown so you learn why each wrong answer is wrong - not just the key.
Sample question
From the free tier of the ScoreMint AP Physics 1 bank - try it, then check the answer.
A swimming pool is filled with water (). What is the gauge pressure at a depth of below the surface? Use .
- A.
- B.
- C.
- D.
Show answer and explanation
Answer: B. Gauge pressure at depth in a fluid of density is . This represents the pressure due to the fluid column above that point, not including atmospheric pressure. Pa. The absolute pressure at this depth would be Pa.
Study tip
The buoyant force uses the fluid's density and the displaced volume - never the object's density. A floating object displaces its weight in fluid; a sunken one displaces its volume.