Stress and Pressure are both words that are commonly mistaken for one another. We can define pressure as the amount of force that is exerted per unit area. On the other hand, stress refers to the amount of force exerted per unit area, experienced by a material. The difference between stress and pressure can help us to understand the basics better and know their comparisons thoroughly. Let us now understand what is the difference between stress and pressure.
What is Stress?
The amount of force per unit area experienced by a material is termed as stress.
What is Pressure?
The pressure is the amount of force applied per unit area.
Difference between Stress and PressureÂ
                                        Difference between Stress and Pressure
The important difference between stress and pressure.
| Parameters | Stress | Â Â Â Â Â Â Â Â Â Â Â Â Â Pressure |
| Definition | The internal resistive force to the deformation per unit area is termed as stress. | The amount of force applied per unit area is termed as pressure. |
| Representation | Stress can be represented as (strain) / (Young’s modulus) | Pressure can be mathematically represented as (force) / (area) |
| Property | Stress is a material property. | The pressure is a unique property of thermodynamics or physics |
| Sign | Stress can be either a positive or a negative force | The pressure is always a positive force |
| Measurement | There is no device to measure stress (not a measurable quantity). Stress is calculated by measuring strain or elongation. | The pressure is physically measured (measurable quantity) using pressure gauges, manometers, and other pressure measuring devices or instruments. |
| Types | Stress may be tensile, compressive and shear | The pressure is always compressive |
| Magnitude | The magnitude of stress at a point in a different direction is different. | The magnitude of the pressure at a point in all the directions remains the same. |
| Area dependency | Â Stress varies with change in surface area. | The pressure is independent of the area of the contact surface. It remains constant and does not vary with change in surface area. |
| Application | Stress develops internally | The pressure exerts externally |
After learning about the difference between stress and pressure, it is important to know the details of stress and pressure thoroughly.
Stress
The internal force acting over a cross-sectional area within the material is termed as stress. Stress is developed only when an external force acted upon and tries to disturb the equilibrium position. For example, when someone pulls the spring, stress is developed in it, which tries to retain its original position. We relate stress to material engineering where it is used with regard to the wires and sheets.
When we applied force on the body, it tries to change the original shape of the body by changing its interatomic distance. However, it is the tendency of the body to oppose the external force so that it can maintain its original shape, Due to this tendency opposite force developed inside the body. This opposite force developed per unit is termed as stress.
Stress direction is opposite to external force. Stress has a structural property. It developed within a body to resist an external force. The stress can be different in different directions inside the solid.
Pressure
A force applied per unit area typically used inside a fluid is termed as pressure. It is the same in all directions at a point inside the fluid. We use pressure in situations of mechanical things where a certain amount of pressure is applied in a hydraulic machine.
The pressure is the force that is an object exerts on the area that it influences. For example, imagine a ball hitting a wall. As the ball hits the wall, it exerts pressure on the wall. The pressure belongs to the thermodynamic property. The pressure is thus a scalar quantity. It also relates the vector area element (a vector normal to the surface) with the normal force acting on it.
The pressure is an intrinsic property and most of the time related to fluids. It depends on the momentum transfer between the atoms of a liquid or gas volume (molecules constrained inside the volume) on a micro-scale.
FAQs about Stress and Pressure
Q1. In physics, is stress the same as pressure?
Answer: Stress is the same as pressure, the difference is the force in pressure is external but the force in stress is internal which stops it to change its shape or size.
Q2: What are the different units of pressure in meteorology?
Answer:Â The pressure units most commonly used by meteorologists in the United States are inches of mercury and millibars. In countries that commonly use SI units, typically report atmospheric pressures in kiloPascals.
Q3. Is pressure is always compressive in nature?
Answer: Pressure always acts normal to a surface and it is always compressive in nature. We, therefore, need only its magnitude for its complete description. Hence, the direction is always normal to the surface, and the magnitude of force acting depends upon the particular area acting.
References
https://www.britannica.com/science/stress-physics
https://www.britannica.com/science/pressure
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