Difference Between Stress and Pressure in Physics, Examples, Application
Difference between stress and pressure: Pressure is defined as the force applied per unit area. Stress refers to the force per unit area experienced by a material.
Krati Saraswat27 May, 2025
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Difference Between Stress and Pressure: The terms stress and pressure are often used interchangeably, but they have distinct meanings. Pressure is defined as the level of force exerted per unit area.
In contrast, stress refers to the amount of force applied per unit area by a substance. Pressure is commonly associated with fluids and is an intrinsic property influenced by momentum transfer between atoms or molecules within a liquid or gas volume on a micro-scale. Stress, however, results from a body's tendency to revert to its reference state after experiencing random deformation, and it occurs when a force is applied to cause deformation. These nuances highlight key differences between stress and pressure. Continue reading to explore further distinctions between these two concepts.| NEET Physics Syllabus | NEET Physics Important Questions with Answers |
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Difference Between Stress and Pressure Overview
Distinguishing between stress and pressure is crucial, as these terms are frequently confused. Pressure is primarily characterized as the force applied per unit area. In contrast, stress pertains to the force exerted per unit area experienced by a material. This distinction is crucial, defining stress as fundamentally different from pressure. By comprehending the significant variances between stress and pressure, one can discern the key factors setting them apart. Notably, pressure is an external influence acting on an object from the outside, while stress affects the object internally. For a more in-depth understanding of stress, it is essential to explore the relationship between stress and strain.Difference Between Stress and Pressure
The table below shows the difference between stress and pressure :|
Difference Between Stress and Pressure |
|||
|---|---|---|---|
| Sr. No. | Feature | Stress | Pressure |
| 1 | Definition | Internal force experienced by a material due to deformation | Force applied perpendicular to the surface of an object |
| 2 | Symbol | σ (sigma) | P (capital letter "P") |
| 3 | Direction | Can act in any direction | Acts perpendicular to the surface |
| 4 | SI Unit | Pascal (Pa) | Pascal (Pa) |
| 5 | Formula | Stress (σ) = Force (F) / Area (A) | Pressure (P) = Force (F) / Area (A) |
| 6 | Types | Tensile stress, compressive stress, shear stress, etc. | Atmospheric pressure, fluid pressure, etc. |
| 7 | Nature | Affects the internal structure of a material | Acts on the surface of an object |
| 8 | Measurement | Measured in force per unit area | Measured in force per unit area |
| 9 | Application | Used in material science and engineering | Applied in various fields including physics, fluid dynamics, and engineering |
What is Stress?
Stress is the measure of the vital force exerted per unit area on a body. Tensile stress arises when external forces pull on an object, causing elongation akin to the stretching of an elastic band. Conversely, compressive stress occurs when forces compress an object. Bulk stress is evident in a uniformly pressured body from all sides, such as a submerged submarine. In certain instances, forces may induce visible deformation without being purely tensile or compressive. Shear forces, operating tangentially to an object's surface, create shear stress. The stress formula in physics and technology defines stress (σ) as the force per unit area within a material due to externally applied forces. It accurately models flexible elastic, plastic, and fluid behaviors. The stress formula is represented as:σ=FA
Here, the stress units are determined by the units of force and area. The SI unit of stress is the pascal (Pa), where 1 Pa=Nm21Pa=m2N. Let's consider a simple example to understand stress: a hanging rope. Imagine you have a rope hanging vertically, and you decide to hang a weight at the bottom of the rope. In this scenario, the weight exerts a force on the rope. The stress in this context can be explained as follows:- Force (F): The weight you hang on the rope applies a force downward due to gravity.
- Area (A): In this case, the cross-sectional area of the rope bearing the weight. For simplicity, let's assume the rope has a uniform cross-sectional area.
σ = AF
- σ (stress) is the force per unit area.
- F is the force applied (the weight of the hanging object).
- A is the cross-sectional area of the material (the rope in this case).
- If the weight is small, the stress on the rope will be relatively low.
- The force increases as the weight increases, leading to higher stress on the string.
- If the weight becomes too large, the stress may exceed the rope's tensile strength, and the cord could break.
Application of Stress
The application of stress, particularly in the context of materials and engineering, is crucial for various purposes. Here are some notable applications of stress:What is Pressure?
Pressure is the force applied per unit area commonly employed within fluids. This force is uniformly distributed in all directions at a specific point within the fluid. In mechanical applications, pressure finds utility, especially in hydraulic machines where specific pressures are applied. Pressure is the force exerted by an object on the area it influences. Consider the scenario of a ball striking a wall; the impact on the wall creates pressure. This property falls under the realm of thermodynamics and is scalar. It establishes a connection between the vector area element (a vector normal to the surface) and the corresponding normal force acting upon it. Primarily an intrinsic property, pressure is frequently associated with fluids. Its determination relies on the momentum transfer between the atoms within a liquid or gas volume, with molecules confined within that volume on a micro-scale. Let's consider a practical example to understand pressure: a balloon.- Force (F): The force you blow into the balloon is exerted by the air. The air molecules collide with the inner surface of the balloon, creating a force.
- Area (A): The area is the balloon's surface in contact with the air molecules. As the balloon inflates, this area increases.
- P (pressure) is the force per unit area.
- F is the force applied (the air pressure inside the balloon).
- A is the cross-sectional area of the balloon.
- When you start inflating the balloon, you can feel it becoming tighter. This is an indication of increased pressure inside the balloon.
- The force that the air molecules exert will increase as you inflate the balloon, increasing the pressure inside of it.
- The balloon could explode if the pressure builds up too much, emphasizing how crucial it is to comprehend pressure to maintain the integrity of materials.
Applications of Pressure
The application of pressure is widespread and plays a crucial role in various fields. Here are some notable applications of pressure:
Difference Between Stress and Pressure FAQs
How is stress defined in terms of mechanics?
In mechanical terms, stress is defined as the internal force per unit area within a material. It is the result of applied forces that cause deformation or strain.
How does stress relate to material properties?
The amount of stress a material can handle without permanent deformation or failure is determined by its material properties, such as tensile strength and elasticity.
Are stress and pressure measured in the same units?
While stress is also measured in Pascals (Pa) or similar units, the context may require different units like psi (pounds per square inch) or N/m². Pressure is consistently measured in Pascals.
How is stress distributed within an object?
Stress can be distributed uniformly or vary across different sections of an object, depending on factors like geometry, material properties, and applied forces.
Can you provide real-world examples of stress and pressure?
Stress is observed in structures like bridges or buildings under load, where internal forces cause deformation. Pressure is evident when standing on the ground, with the weight distributed over the surface area of the feet.
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