Grade 8 ↓
Pressure and its applications
Pressure is a concept we encounter in many aspects of our daily lives, yet it is not something we think about very often. Whether we are getting out of bed in the morning or riding a bicycle, pressure plays an important role. In physics, understanding pressure and its applications helps us explain and predict many phenomena in nature and technology.
What is the pressure?
Pressure is the force applied to a surface per unit area. Mathematically, pressure can be defined using the formula:
Pressure (P) = Force (F) / Area (A)Where:
- Pressure (P): Measured in Pascal (Pa).
- Force (F): Measured in Newtons (N).
- Area (A): Measured in square metres (m²).
For example, if a force of 10 newtons is applied over an area of 2 square meters, the pressure applied would be:
P = 10 N / 2 m² = 5 PaIn everyday language, when you push an object with your hand, you are applying pressure. The harder you push and the smaller the area of the object being pushed, the more pressure you are applying.
Illustration of pressure
In the figure above, the downward arrow represents the force applied to a rectangular area. The smaller the area or the greater the force, the greater the pressure.
Units of pressure
The SI unit of pressure is the pascal (Pa). However, there are other units of pressure you may encounter:
- Bar: 1 bar = 100,000 Pa
- Atmosphere (atm): 1 atm ≈ 101,325 Pa
- Millimeters of mercury (mmHg): commonly used in medicine and meteorology
Remember that 1 pascal is a very small unit of pressure, and in practice, pressure is often measured in kilopascals (kPa), where 1 kPa = 1,000 Pa.
Exploration of pressure in fluids
Fluids include both liquids and gases. In fluids, pressure is exerted equally in all directions because the molecules are able to move freely. This phenomenon is known as Pascal's law, which states that pressure applied to an enclosed fluid is transmitted throughout the fluid without decreasing.
An interesting example of Pascal's law is hydraulic lift. In hydraulic lift, a small force applied to a small piston produces a large force on a large piston, because the pressure is spread evenly.
Example of Pascal's law
This diagram shows a hydraulic lift with a small piston on the left and a large piston on the right. Applying a small force to the small piston results in a large force on the large piston.
Applications of pressure
Pressure has wide applications in various fields of human activities. Let's look at some real-life examples where pressure is used:
1. Car tires
Car tires require the right amount of air pressure to work effectively. Properly inflated tires ensure good contact with the road, which increases safety and fuel efficiency. If the pressure is too low, it can increase friction and cause tire wear. On the other hand, high pressure can make tires more susceptible to punctures.
2. Syringe
Syringes use pressure to pull fluid in and out. When you pull back the syringe's plunger, you decrease the pressure inside, which draws fluid in. Pushing the plunger increases the pressure inside, which forces fluid out.
3. Hydraulic brake
Hydraulic brakes in vehicles are an application of fluid pressure. When you press the brake pedal, it increases the pressure in the brake fluid, which then moves to the brake pads and stops the car. This makes it possible to stop the car with relatively little force from the driver.
Factors affecting pressure
Several factors affect the pressure exerted by or on an object:
- Force: If area remains constant then increase in force increases pressure.
- Area: When force remains constant then reduction in area on which force is applied increases pressure.
These factors are important in the design of equipment and machinery, where controlling the pressure can improve efficiency and functionality.
Atmospheric pressure
Atmospheric pressure is the pressure exerted by the weight of the air in the Earth's atmosphere. It decreases with altitude because there is less air to exert force upward. At sea level, atmospheric pressure is about 101,325 Pa (or 1 atm).
Example of atmospheric pressure
This diagram shows the Earth and its atmosphere. The weight of the gases in the atmosphere exerts pressure on the Earth's surface.
Applications of atmospheric pressure
Atmospheric pressure plays a role in a variety of natural and technological processes:
1. Breathing
Humans and animals breathe because of differences in air pressure. When the diaphragm contracts, it makes the pressure inside the lungs lower than outside, allowing air to come in. Exhaling increases the pressure in the lungs, forcing air out.
2. Weather patterns
Atmospheric pressure affects weather conditions. High pressure systems usually bring clear weather, while low pressure systems can cause clouds and precipitation. Meteorologists use changes in atmospheric pressure to predict the weather.
Measuring pressure
Pressure can be measured using a number of instruments, common of which are:
- Barometer: Used to measure atmospheric pressure. It usually uses mercury or aneroid mechanism.
- Manometer: Used to measure gas pressure in closed systems.
Example of a barometer
This figure shows a simple barometer. The height of the liquid column in the tube helps determine atmospheric pressure.
Conclusion
Understanding pressure and its applications helps us better understand the physics behind many everyday phenomena and technologies. From the way our transportation depends on pressure systems to the basic function of our bodily organs, pressure is an essential concept in both natural and engineered systems.
By understanding the fundamental aspects of pressure, such as how it acts within fluids and affects structures, it is possible to make informed observations and decisions in a variety of scientific and practical contexts.
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