Pressure
Overview
A sharp knife slices easily while a blunt one tears, a camel crosses soft sand on its broad feet, and a deep-sea diver feels the water squeeze harder the deeper they go. All three are about pressure: how a force is shared over an area, and how a liquid presses on whatever is beneath its surface.
In this topic you will define pressure, use the equation linking force and area, and explain everyday examples where changing the area changes the effect of a force. You will then look beneath a liquid surface, see qualitatively how pressure grows with depth and density, and use the Supplement equation for the change in pressure in a liquid.
Objectives
- Define pressure as force per unit area; recall and use the equation F p = A
- Describe how pressure varies with force and area in the context of everyday examples
- Describe, qualitatively, how the pressure beneath the surface of a liquid changes with depth and density of the liquid
- [Supplement] Recall and use the equation for the change in pressure beneath the surface of a liquid ∆p = ρg∆h
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Pressure. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- A force of 40 N acts on an area of 0.5 m^2. The pressure is: A. 20 Pa B. 80 Pa C. 0.0125 Pa D. 40 Pa Answer: B
- The SI unit of pressure is the: A. newton B. joule C. pascal D. watt Answer: C
- Pressure beneath a liquid surface increases with: A. depth and density B. width of container only C. surface area only D. colour of the liquid Answer: A
- A diver is 10 m deep in water of density 1000 kg/m^3 (g = 9.8 N/kg). The increase in pressure is: A. 980 Pa B. 9800 Pa C. 98000 Pa D. 100 Pa Answer: C
- Why does a sharp knife cut more easily than a blunt one? A. it has more mass B. its small edge area gives higher pressure C. it is heavier D. it has lower density Answer: B
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Recommended Books
Further learning from open sources
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Textbook section
Pressure
You have no doubt heard the word pressure being used in relation to blood (high or low blood pressure) and in relation to the weather (high- and low-pressure weather systems). These are only two of many examples of pressures in fluids. Pressure P P size 12{P} {} is defined as where F F size 12{P} {}
"College Physics: Pressure" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/11-3-pressure. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
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Textbook section
Variation of Pressure with Depth in a Fluid
If your ears have ever popped on a plane flight or ached during a deep dive in a swimming pool, you have experienced the effect of depth on pressure in a fluid. At the Earth’s surface, the air pressure exerted on you is a result of the weight of air above you. This pressure is reduced as you climb u
"College Physics: Variation of Pressure with Depth in a Fluid" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/college-physics/pages/11-4-variation-of-pressure-with-depth-in-a-fluid. Access for free at https://openstax.org/books/college-physics/pages/1-introduction
Published by other organisations under open licences, credited as they ask. Links open their websites.
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