Difference between force and stress

One of the key point that shows force and stress differ from each other is that the force is responsible for the deformation in the object while stress shows a measure of resistance to the deformation developed by the object.

Before moving toward our main topic, let’s know about the force and stress in brief.

Force:

Force is a push or pull action that can create motion in the object or resist the motion of the object.
Force is a vector quantity and it is denoted by the symbol ‘F’.

The force can arise due to the acceleration into the mass, gravitational or magnetic action, etc.

Example: As shown in the figure, the force acting on the ball provides acceleration to the ball which is equivalent to the product of its mass and acceleration.

Thus the force acting on the ball is given by,

Stress:

Stress is the internal resistance per unit resisting area developed by the object to resist the deformation. It is given by the ratio of internal resisting force to the area of cross-section.

The stress is not a scalar nor a vector quantity as it is considered as tensor quantity.

Example: As shown in the below figure, the man is stretching the rubber by applying the force ‘F’. To resist the deformation, the rubber is also developing the resistance force and this resistance force per unit cross-sectional area is the stress developed into the rubber.

\sigma = \frac{\text{Resistance force} (F_{R})}{\text{Cross sectional area} (A)} = \frac{F}{A} ——(∵F = F_{R})

Difference between force and stress:

FAQs:

1. Are stress and force same?

No, stress and force are different terms.

2. How is stress related to force?

The relation between the stress and force is given by the following formula.
Stress = (Force) / (Resisting area)

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Pratik is a Graduated Mechanical engineer. He enjoys sharing the engineering knowledge learned by him with people.