Pressure is a fundamental concept in physics that plays a crucial role in various phenomena and engineering applications. Understanding atmospheric pressure is essential as it influences weather patterns and atmospheric dynamics. Atmospheric pressure refers to the force per unit area exerted on a surface by the weight of the air above that surface. The standard unit of pressure in the International System of Units (SI) is the pascal (Pa). Measurement of pressure is commonly done using instruments such as the mercury barometer, aneroid barometer, and manometer. A mercury barometer utilizes the height of a mercury column to determine atmospheric pressure, while an aneroid barometer uses the deflection of a flexible metal cell. The manometer, on the other hand, measures pressure differences in closed systems. One intriguing feature of atmospheric pressure is its variation with height. As altitude increases, atmospheric pressure decreases due to the reduced weight of the air column above. This variation is crucial in aviation and weather forecasting. Barometers are also used as altimeters to estimate altitude based on the surrounding pressure. Moving on to pressure in liquids, the relationship between pressure, depth, and density in a liquid is given by P = ρgh, where P is the pressure, ρ is the density of the liquid, g is the acceleration due to gravity, and h is the depth of the liquid. Moreover, Pascal's Principle states that a change in pressure applied to an enclosed fluid is transmitted undiminished to all portions of the fluid. This principle finds applications in hydraulic systems, such as hydraulic jacks and brakes, where a small force applied to a small area can generate a large force on a larger area. In conclusion, understanding pressure, both in the atmosphere and in liquids, is fundamental for various scientific and practical applications. It allows us to make sense of atmospheric phenomena, design hydraulic systems, and comprehend the behavior of fluids under different conditions. Mastering the concepts of pressure equips us with the knowledge to solve complex problems and engineer innovative solutions in diverse fields of study and industry.


  1. Relate the variation of pressure to height
  2. Apply the principle of transmission of pressure in liquids to solve problems
  3. Use a barometer as an altimeter
  4. Identify pressure measuring instruments
  5. Recognize the SI units of pressure (Pa)
  6. Determine and apply the principle of pressure in liquid
  7. Determine the relationship between pressure depth and density

Lesson Note

Pressure is a fundamental concept in physics that measures the amount of force exerted per unit area. It is an essential aspect of various phenomena in both natural and industrial contexts. The study of pressure helps us understand how gases and liquids behave under different conditions, how weather changes occur, and even how various instruments work.

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.

  1. A gas exerts pressure due to the
  2. A. Random motion of its molecules
  3. B. Attraction between its molecules
  4. C. Constant volume
  5. D. Low temperature
  6. Answer: A. Random motion of its molecules
  7. The SI unit of pressure is
  8. A. Newton
  9. B. Pascal
  10. C. Joule
  11. D. Kilogram
  12. Answer: B. Pascal
  13. The device used to measure atmospheric pressure is called a
  14. A. Thermometer
  15. B. Hydrometer
  16. C. Barometer
  17. D. Speedometer
  18. Answer: C. Barometer
  19. Which of the following is a unit of pressure?
  20. A. kg
  21. B. m/s
  22. C. W
  23. D. N/m²
  24. Answer: D. N/m²
  25. The principle that explains the transmission of pressure in liquids is known as
  26. A. Boyle's Law
  27. B. Archimedes' Principle
  28. C. Pascal's Principle
  29. D. Hooke's Law
  30. Answer: C. Pascal's Principle
  31. How does pressure change as we go higher in the atmosphere?
  32. A. Increases
  33. B. Decreases
  34. C. Remains constant
  35. D. Fluctuates randomly
  36. Answer: B. Decreases
  37. What instrument can be used as an altimeter to measure height based on atmospheric pressure?
  38. A. Voltmeter
  39. B. Barometer
  40. C. Ammeter
  41. D. Tachometer
  42. Answer: B. Barometer
  43. The relationship between pressure, depth, and density in a liquid is given by the formula
  44. A. P = F/A
  45. B. P = mgh
  46. C. P = V/m
  47. D. P = ρgh
  48. Answer: D. P = ρgh
  49. The SI unit of density is
  50. A. kg/m²
  51. B. m/s²
  52. C. N/m
  53. D. kg/m³
  54. Answer: D. kg/m³
  55. What is the principle that states that a liquid exerts equal pressure in all directions at a given depth?
  56. A. Pascal's Principle
  57. B. Archimedes' Principle
  58. C. Newton's Law
  59. D. Ohm's Law
  60. Answer: A. Pascal's Principle

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Past Questions

Wondering what past questions for this topic looks like? Here are a number of questions about Pressure from previous years

Question 1 Report

Molecules move in random motion within a liquid. The total internal energy of the liquid depends on all of the following except its?

Question 1 Report

Which of the following liquids has the highest surface tension?

Question 1 Report

Which of the following statements about the pressure in a liquid is NOT correct? It

Practice a number of Pressure past questions