The Role Pressure Plays In The Real World

A diagram showing connection currents.

What is pressure, and how does it influence the things we do, see, and hear every day? To address these questions and the importance of pressure in different scenarios, we have to understand the fundamental physics behind the scenes. 

Firstly, pressure is the force per unit area exerted by gas particles colliding with the walls of a container, and it’s calculated by measuring the momentum and frequency of collisions between the particles and the walls of the container. Pressure is typically expressed in pascals (Pa), though atmospheres (atm) and millimeters of mercury (mmHg) are valid units as well. The equation for determining pressure is given below, where “P” is pressure, “F” is force, and “A” is area:

P = F/A

Though not a direct component of the equation above, temperature is also relevant to pressure, as it is proportional to the kinetic energy (force) of gas particles. Increasing the temperature means that the particles can move faster and collide with more frequency and power. The Particle Theory of Matter states that the average kinetic energy of particles goes up with an increase in temperature.

To provide a real-life example of how pressure influences everyday things, think of a balloon. Balloons are inflated if the pressure of the gas within is higher than the pressure outside. This pressure difference can be induced when we pump or blow air into the balloon, thereby introducing more air molecules that collide more frequently with the “walls” of the balloon. However, a balloon can also be inflated—assuming it doesn‘t pop—if the air inside of it is heated. By heating, the gas particles become more energetic and collide with greater force and frequency against the elastic wall of the balloon, causing it to expand. 

Another real-life example would be tires feeling “tighter” after a drive (or the tire pressure going up on your car dashboard). This is often due to the friction that results from the tire grinding against the road as it moves. This friction heats the air inside the tire, increasing the temperature and pressure. Meanwhile, if the tire is punctured, the amount of gas particles inside the tire decreases due to leakage. The pressure goes down as a result, and with fewer air particles pushing against its walls, the tire loses rigidity, leading to reduced support, diminished traction, and poor handling. If driven further, it can even damage the rim and suspension, which is why carrying a replacement tire is important.

Most notably, Formula 1 racing takes the concept of pressure to an extreme, as it is a sport where performance is derived from very specific measurements and techniques. First of all, tire pressure is essential to maintain and adjust based on race conditions. To generate maximum power and handling, it is crucial that the pressure and temperatures of the tires are optimized. Additionally, during each combustion stroke, an air-fuel mixture has to be ignited under high pressure and temperature. This is what causes the pistons in the vehicle‘s engine to be pushed up and down, the energy from which is converted into rotational speed at the wheels.

Pressure is also important to keep in mind in weather forecasting, as pressure differences are what drive heat transfers through conduction, convection, and expansion, forming unique weather patterns and trends. As the Sun heats the Earth’s surface, the heat energy is transferred from the ground to the surrounding air. This conduction warms the air, and as the heating makes the air less dense, it begins to rise and expand, increasing pressure. However, when the air eventually cools down, whether it be after sunset, over a snowfield, or at higher altitudes, its particles lose kinetic energy and slow down. Pressure drops as a result, and the cooled air, being more dense, sinks back to the ground. This process is commonly known as convection currents, and it forms the basis for most weather phenomena.

It’s this understanding of pressure that enables accurate weather forecasting. The movement of air, cloud development, and precipitation are all brought about by atmospheric pressure variations. This is why meteorologists constantly monitor changes in pressure in the atmosphere. Another important concept to know in weather forecasting is that air always travels from high to low pressure. Pressure trends also reveal approaching weather systems; decreasing pressure on the barometer typically means storms and rain, while rising pressure usually means fair weather. Through mapping pressure patterns over a period of time, forecasters are able to predict temperature changes and extreme weather events, giving communities valuable time to prepare.

In the kitchen, pressure is as crucial for baking bread as it is for meteorologists forecasting storms. When yeast ferments, carbon dioxide gas is produced, and it gets trapped inside the dough’s elastic gluten surface. Heat is transferred from the metal pan in the oven to the inside of the dough, which raises the temperature of the gas and water within. The warmer gas molecules within the dough move faster, exerting more outward pressure on the dough. So if you’re baking bread and see the dough expanding, this is exactly why!

As it can be seen, pressure plays an important role in many real-life activities and processes. It controls our weather, cloud formation, and wind patterns, and it allows meteorologists to make accurate forecasts. On the race track, it maximizes tire grip and engine power, while in the kitchen, it turns dough into puffy, delicious bread. In conjunction with other components of thermodynamics, pressure helps us to better understand day-to-day occurrences and makes it possible for us to innovate and make things comfortable, safer, and more efficient.