# How do I calculate the factor of safety for a prismatic bar under tension?

• Kazaam
In summary, the conversation discusses a homework question about a prismatic bar in tension. The load applied on both ends is 37 N, with a cross section area of 5.7 cm^2 and an allowable stress of 100 kPa. The question asks for the factor of safety for the system, with the expected answer being 1.541 kPa. However, the person discussing the question is confused about how to arrive at this answer and asks for clarification on the correct equation and units for the safety factor.

#### Kazaam

There is a question on my home work that I just don't understand how they got the answer they did.

The first question is:
In a prismatic bar, the load applied on both ends is 37 N causing the member to be in tension. If the cross section area of the member is 5.7 cm2 and the allowable stress is 100 kPa. What is the factor of safety for the system?

I got .1.298 kpa, the answer is supposed to be 1.541 kpa, how does (37N/.057)/100 kpa= 1.541 Kpa, what am I missing here?

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Kazaam said:
There is a question on my home work that I just don't understand how they got the answer they did.

The first question is:
In a prismatic bar, the load applied on both ends is 37 N causing the member to be in tension. If the cross section area of the member is 5.7 cm2 and the allowable stress is 100 kPa. What is the factor of safety for the system?

I got .1.298 kpa, the answer is supposed to be 1.541 kpa, how does (37N/.057)/100 kpa= 1.541 Kpa, what am I missing here?
5.7 cm^2 = 0.00057 m^2. And then you incorrectly have written that F.S. = actual stress/allowable stress...what should that equation be??. And what are the units of the safety factor?

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## 1. What is shear force and why is it a problem?

Shear force is a type of internal force that acts parallel to a material's cross-sectional area. It is a problem because it can cause a material to deform or fail when it exceeds the material's strength.

## 2. How is shear force calculated?

Shear force is calculated by taking the sum of all the external forces acting on a material in a specific direction.

## 3. What are the common causes of shear force?

Shear force can be caused by external forces such as wind, gravity, or applied loads. It can also be caused by changes in temperature or stress within a material.

## 4. How can shear force be reduced or prevented?

Shear force can be reduced or prevented by using materials with higher strength, limiting the amount of external force applied, or by using reinforcement techniques such as adding additional supports or bracing.

## 5. How does shear force affect different types of materials?

Shear force affects different materials in different ways. For example, brittle materials such as glass or ceramics are more prone to failure under shear force, while ductile materials like steel are able to withstand higher levels of shear force before failing.