Fluids

Fluids are matter that flows, liquids and gases both. Four ideas carry the unit. Density is a property of the substance, not the sample. Pressure climbs with depth and depends on density, not on the shape of the container. The fluid pushes up on anything sitting in it, and a comparison of densities decides whether the object floats or sinks. And in moving fluid, a narrower channel speeds the flow while the faster flow drops the pressure.

Topics

8.1

Internal structure and density

Pressure

Buoyancy

Fluid Flow

Lesson

Diagnostic

after diagnostic

Equations For every problem in this unit

Density

$\rho = \dfrac{m}{V}$

Pressure

$P = \dfrac{F_\perp}{A}$

Pressure at depth

$P = P_0 + \rho g h$

Gauge pressure

$P_\text{gauge} = \rho g h$

Buoyant force

$F_b = \rho V g$

Continuity

$A_1 v_1 = A_2 v_2$

Bernoulli's equation

$P_1 + \rho g y_1 + \dfrac{1}{2}\rho v_1^2 = P_2 + \rho g y_2 + \dfrac{1}{2}\rho v_2^2$

Unit 8 tools

Challenge bank

1 / 60

60 open-ended problems.

Read the question, work it out, then flip the card to compare your reasoning to the worked solution. Mark each card so you can return to the ones that still bite.

Question

Tap card to reveal explanation

Worked solution

Tap card to return to question

Cumulative assessment

Test the unit.

Twenty mixed items pulled from across all 4 topics. Identifies which misconceptions still bite when you cannot see which topic the question came from.

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Check what stuck.

Units 1 through 8, drawn evenly so earlier units get the same share as this one. Twenty questions or a full 42-question section, your choice. Even coverage means this is a retention check rather than a score estimate.

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Pressure and depth lab

Collect your own data, choose the transform that straightens the plot, and read a fluid density off the slope. Results record to your class dashboard.

Open the lab →