PRESSURE
1. Context
Once you start seeing the effects of pressure somewhere, you will start realising it is actually everywhere. The water in your tap, the clouds that suddenly appear on a sunny day, or the fact you can drive your bike or car on those wheels
2. What is Pressure?
- Pressure is defined as the force exerted per unit area on a surface. It is a scalar quantity, meaning it has magnitude but no direction. Pressure is a fundamental concept in physics and engineering, applicable in various contexts such as gases, liquids, and solids
Formula: P = F/A, where:
P = Pressure
F = Force applied perpendicular to the surface
A = Area of the surface
P = Pressure
F = Force applied perpendicular to the surface
A = Area of the surface
- Pressure is the way the microscopic world interacts with us. Although we can't see the billions of atoms and molecules in the air around us, they constantly collide with us, creating what we know as air pressure.
- For instance, when you are on a flight and there's a risk of a decrease in the number of air molecules around you, the flight attendant might say, "the pressure may drop, please use an oxygen mask."
- If you want to cook something and need the air molecules to be more energetic to heat your food more effectively, you use a pressure cooker.
- Before placing your vegetables in the cooker, you add water, which heats up and the water molecules then collide with your carrots and potatoes, breaking their molecular bonds and cooking your food.
- By keeping all these molecules contained in a strong metal vessel from which they cannot escape, you increase the pressure
3. Force and Pressure
- Pressure and force are closely interconnected. You may recognize Isaac Newton as a renowned physicist with distinctive long hair, and the fundamental unit of force is named after him: the newton (N).
- Units are used to measure various quantities, such as metres for distance, kilograms for weight, and litres for volume. Similarly, force — like the action of pushing or pulling a door — is measured in newtons.
- For instance, a small apple weighing around 100 grams exerts a force of about 1 N on your hand. If you weigh 50 kilograms after intermittent fasting, you can say you weigh approximately 500 N instead.
- Pressure is the average force distributed over a given area. For example, if you place a heavy book on your palm, and then try holding the same book with just one finger, the weight of the book remains constant, but it feels heavier on your finger because it is concentrated on a smaller area.
- The pascal (Pa) is the unit used to measure pressure. One pascal is a relatively small amount of pressure.
- For example, an apple resting on your hand exerts a pressure of about 500 Pa. The air above us, extending up to space, exerts a pressure of 100,000 Pa, which is equivalent to the pressure exerted by about 200 apples on your hand.
- All fluids, including blood, have pressure. Blood molecules collide with the walls of our arteries at varying speeds, creating pressure. When your blood pressure is measured, the doctor provides readings such as 120/80, which represent pressure, though not in pascals
4. Examples of Pressure
- Just as atmospheric pressure is roughly equivalent to the weight of about 200 small apples, it can also be compared to a specific amount of liquid. For instance, when you are approximately 10 meters underwater, the pressure exerted by the water on your body (in addition to the psychological pressure from the inability to breathe) matches that of the atmospheric pressure.
- When measuring blood pressure, if you pay attention, the doctor places a cuff around your upper arm and pumps air into it. The goal is to increase the air pressure in the cuff to match the pressure of the blood flowing through your arteries, then slowly release it. In older blood pressure devices, this pressure in the cuff was balanced using a liquid column in a tube.
- The pressure in our blood is about one-fifth of the atmospheric pressure. To measure this using water, you would need a two-meter column of water, which is impractical to carry around. Therefore, a heavier liquid was sought, requiring a smaller volume to achieve the same pressure balance, making the devices more portable.
- Mercury, being about 15 times denser than water, allows for this convenience. The blood pressure readings of 120/80 given by doctors refer to millimeters of mercury: 120 mm when the heart beats (systolic pressure) and 80 mm when the heart rests between beats (diastolic pressure)
5.Way Forward
Transition to advanced, portable electronic blood pressure monitors that do not rely on mercury. These devices use oscillometric or digital sensors and are more convenient and safer. They reduce the need for mercury, which is hazardous and requires special handling and disposal.
Encourage the development and use of alternative fluids in sphygmomanometers (blood pressure cuffs) that are non-toxic and environmentally friendly. Research into suitable non-mercury liquids or other technologies should be supported to ensure accurate and safe pressure measurements
Source: The Hindu
