We all like having running water available at the turn of a knob, but what's causing the water to flow? We can thank civil engineers and their knowledge of pressure, flow and Bernoulli's principle for designing systems that connect large bodies of water to every kitchen faucet.
So far we've learned how fluid behaves when it's not moving, known as hydrostatics. Now less learn about how fluid moves and hydrodynamics.
In this lesson we'll cover how a difference in pressure causes fluid to flow. We'll also learn how to describe flow using a few simple equations that include volume, time, area and velocity. Since ideal fluids are incompressible, we'll see how a change in flow area results in a change in velocity.
We'll cover Bernoulli's equation, which is based on the law of conservation of energy that we already learned. The total amount of mechanical energy (the sum of the kinetic energy, gravitational potential energy and internal or pressure energy) is the same at any point along the flow, which will be really useful in describing flow.
We'll also learn how to derive Torricelli's law, a specific application of Bernoulli's principle, which describes the speed of a fluid shooting out of a hole in a container, and how the fluid moves faster at greater depths.
Answers
Free-Response Questions
Fluids (previously in AP Physics 2)
Note: These are questions from AP Physics 2 exams before 2025. For some questions only parts of the question are relevant to the Fluids unit in AP Physics 1 as noted below.
We all like having running water available at the turn of a knob, but what's causing the water to flow? We can thank civil engineers and their knowledge of pressure, flow and Bernoulli's principle for designing systems that connect large bodies of water to every kitchen faucet.
So far we've learned how fluid behaves when it's not moving, known as hydrostatics. Now less learn about how fluid moves and hydrodynamics.
In this lesson we'll cover how a difference in pressure causes fluid to flow. We'll also learn how to describe flow using a few simple equations that include volume, time, area and velocity. Since ideal fluids are incompressible, we'll see how a change in flow area results in a change in velocity.
We'll cover Bernoulli's equation, which is based on the law of conservation of energy that we already learned. The total amount of mechanical energy (the sum of the kinetic energy, gravitational potential energy and internal or pressure energy) is the same at any point along the flow, which will be really useful in describing flow.
We'll also learn how to derive Torricelli's law, a specific application of Bernoulli's principle, which describes the speed of a fluid shooting out of a hole in a container, and how the fluid moves faster at greater depths.
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