Pressure is something that you observe in Pressure cookers, exam pressure, work pressure, and so on; however, if you talk about pressure in Physics, it makes a difference but how?
Well, in Physics, we define pressure as the physical force exerted on the object.
Also, we can define it as the perpendicular force applied per unit area of the object. And, when we say, a perpendicular force, we mean to say, it is stress.
In this article, we will start with the pressure and stress difference following the explanation.
Note: One thing to note is when pressure and stress are caused by applying a force, then how we can differentiate between stress and pressure? Quite confusing, right?
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We will proceed with the major difference in pressure and stress, following the real-life examples, and further explain these two in detail.
Difference Between Stress and Pressure
Differentiate Pressure from Stress
Let’s suppose that you have a vessel filled with water and keep it on the fire and cover the vessel with a lid. Now as the temperature rises, the lid starts vibrating. You might have observed this happening while preparing a steamed food item.
The science behind it is, at the microscopic level, water has millions of molecules bonded together with the interatomic force of attraction, as the temperature rises, the bond between the molecules break and they start colliding with each other and at the surface of the vessel, which, in turn, creates pressure at the walls of the vessel.
Even if you take the case of a U-shaped jar, fill it with gas, and attach a piston to its top. Now, as you push the piston inwards, the gas molecules expand because of the collision between them.
In Bernoulli’s principle, we learned that the velocity difference between the upper and the lower stream of the fluid creates a pressure difference, and this principle is useful in generating an airlift.
According to these three examples, we understand that pressure occurs in three things viz: liquid, gas, and fluids.
The different types of pressure are absolute pressure, atmospheric pressure, differential pressure, overpressure, or gauge pressure.
If we talk about stress, it is a force applied perpendicular to the area, so it is clearly related to the matter.
Let’s suppose that there is a block of mass ‘m’ placed horizontally. Now, if you apply a force, stress acts at a point of the plane. Since stress acts at a point on the plane of the block, that’s why we consider stress as the force acting per unit area of the plane.
Since stress has three parameters to define it as the vector quantity. These are the magnitude, direction, and point of application. We also called stress the ‘Second-order tensor’.
Task to Do
So, the difference between pressure and stress is easy-to-comprehend when we consider the real-life examples, as we discussed above. So, try to think of a few more real-life examples to understand the pressure stress difference.