AP Physics 1 · Unit 8 · Fluids

Hydrostatics Practice Problems

Follow pressure through connected liquids, interpret column heights, and use hydraulic pressure to find braking torque.

12 questions6 conceptual · 6 calculation

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Simulation scene from the Hydrostatics lesson. — A scene from the related lesson. Open the practice to work through the questions.

What you’ll practice

Build a pressure balance from the actual liquid columns

Separate pressure, volume, and bottom force

Compare equal-depth tanks with different widths and shapes. Explain why equal pressure does not imply equal liquid volumes or equal bottom forces, and account for vertical forces from sloping walls.

Solve connected-column and manometer problems

Choose a shared level in the same liquid, track pressure increases downward and decreases upward, infer an unknown density, and solve a three-liquid differential manometer whose unknown level also changes an upper column.

Connect column height and hydraulic force

Compare a perfect-vacuum barometer with a nonzero vapor-pressure boundary. Transmit gauge pressure between pistons, find a shoe’s friction force, and calculate its braking torque about a drum axle.

A question from this set

Same depth, different shapes

Three open containers hold water to the same depth. A is a straight-sided tank, B is a narrower tank, and C widens toward the top. Their bottom elevations are equal. Which statement correctly separates pressure from volume?

All bottom pressures are equal, but the water volumes can differ.
Equal depth requires equal volume and equal bottom pressure.
The container holding the most water must have the greatest bottom pressure.

Try it in the practice set

Different container shapes can hold different volumes while sharing the same water depth and bottom pressure.

Key ideas

Choose the right common level and boundary pressure

Equal-height pressure needs the same connected liquid

A horizontal comparison through one stationary connected liquid gives equal pressure. Different liquid layers can have different densities and pressure gradients; their interface still has one continuous pressure.

A manometer records a pressure difference

The high-pressure gas depresses its own liquid surface. Use the vertical separation of the free surfaces, then add the atmospheric reference only when an absolute pressure is requested.

See the physics

Compare column measurements and watch a drum brake

After attempting a question, scan equal-level probes through connected liquids, compare both pressure routes in a differential manometer, or measure a barometer column. The hydraulic comparison uses the transmitted pressure to apply a tangential braking force to a rotating drum.

Use a hint for a starting point or open a worked solution to follow the reasoning. Your progress saves in this browser, so you can return to unfinished questions.

Ready for hydrostatics?

Begin with a conceptual question, then work through the calculations.

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