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United StatesPhysics

Unit 8: Fluids

4 dot points across 4 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How do conservation of mass and energy govern a flowing fluid, and why does a fluid speed up where a pipe narrows?

Topic 8.4 Fluids and Conservation Laws: apply the continuity equation and Bernoulli's equation to ideal fluid flow.
A focused answer to AP Physics 1 Topic 8.4, covering the continuity equation A1 v1 = A2 v2 from conservation of mass, Bernoulli's equation from conservation of energy, the inverse speed-area and pressure-speed relationships, and applications to flowing fluids, with full worked examples.
11 min answer →

What is the buoyant force on a submerged object, and how do Newton's laws decide whether it floats or sinks?

Topic 8.3 Fluids and Newton's Laws: apply Newton's laws and Archimedes' principle to objects in fluids, including the buoyant force and floating versus sinking.
A focused answer to AP Physics 1 Topic 8.3, covering the buoyant force from Archimedes' principle F_b = rho V g, applying Newton's second law to a submerged object, the float-versus-sink condition from comparing densities, and apparent weight, with full worked examples.
11 min answer →

What is a fluid, and how does density describe how its mass is distributed?

Topic 8.1 Internal Structure and Density: define a fluid and describe density as mass per unit volume, an intensive property of a substance.
A focused answer to AP Physics 1 Topic 8.1, covering what makes a substance a fluid, density as mass per unit volume, density as an intensive property, the idea of an ideal fluid, and how density compares across substances, with full worked examples.
10 min answer →

How does a fluid exert pressure, and why does pressure increase with depth?

Topic 8.2 Pressure: define pressure as force per unit area and apply the relation between pressure and depth in a static fluid.
A focused answer to AP Physics 1 Topic 8.2, covering pressure as force per unit area, the increase of pressure with depth P = P0 + rho g h, the distinction between absolute and gauge pressure, and how pressure acts in all directions in a fluid, with full worked examples.
11 min answer →