# Shear Force: Help with Question 2(b) - Mentor Note

• smr101
In summary: The maximum BM will occur at the location where the shear force changes sign from + to -.In summary, the solution to the shear force question involves calculating the reactions at the ends of the beam and then using that information to determine the shear force and bending moment at different points on the beam. The maximum bending moment is calculated by finding the location where the shear force changes sign from positive to negative.
smr101
< Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown >

Hi, I'm having problems with the shear force question attached. I've attached the solution as well.

I'm looking at 2. (b), I have the 0 > x > 3 bit, but I'm struggling with the 3 > x > 4 section. Where is the 8 coming from?

Help is much appreciated
.
http://snag.gy/YnZBu.jpg

http://snag.gy/rcA39.jpg

Last edited by a moderator:
smr101 said:
< Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown >

Hi, I'm having problems with the shear force question attached. I've attached the solution as well.

I'm looking at 2. (b), I have the 0 > x > 3 bit, but I'm struggling with the 3 > x > 4 section. Where is the 8 coming from?

Help is much appreciated
.
http://snag.gy/YnZBu.jpg

What calculations have you done to solve this problem? If you had done the basic calculations to determine the reactions at the ends of the beam, the answer to your question would become apparent.

SteamKing said:
What calculations have you done to solve this problem? If you had done the basic calculations to determine the reactions at the ends of the beam, the answer to your question would become apparent.
Yeah, thanks, I've worked it out. In regards to (e) how is the maximum bending moment calculated?

Thanks.

smr101 said:
Yeah, thanks, I've worked it out. In regards to (e) how is the maximum bending moment calculated?

Thanks.

Any location where the shear force is zero is also a location where the BM is either a local maximum or a local minimum.

Hi there,

I can see that you are having trouble with the shear force question in the attached image. In order to understand where the 8 is coming from, we need to look at the concept of shear force and how it is calculated.

Shear force is the force that acts parallel to the cross-section of a material, causing it to slide or shear. In order to calculate the shear force at a particular point, we need to consider all the forces acting on the material before that point.

In this question, we are given a simply supported beam with a point load of 8 kN at 3m from the left support. This means that there is a downward force of 8 kN acting on the beam at 3m from the left support.

Now, when we consider the section between 3m and 4m, we need to take into account the point load of 8 kN as well as the reaction force from the left support. The reaction force at the left support is equal to the sum of all the forces acting on the beam to the left of that point.

In this case, there is only one force acting on the beam to the left of 3m, which is the point load of 8 kN. Therefore, the reaction force at the left support is also 8 kN. This is where the 8 comes from in the shear force diagram for the section between 3m and 4m.

I hope this helps to clarify where the 8 is coming from in the shear force diagram. Keep in mind that shear force is always calculated by considering all the forces acting on the beam before the point in question.

Let me know if you need any further clarification or assistance with this question. Good luck with your studies!

Best regards,

## What is shear force?

Shear force is a type of force that acts parallel to a surface, causing the surface to slide or shear.

## How is shear force calculated?

Shear force is calculated by taking the sum of all the forces acting parallel to a given surface, and then taking the difference between the forces acting on either side of the surface.

## Why is shear force important in engineering?

Shear force is important in engineering because it helps engineers design and analyze structures for stability. It also plays a crucial role in determining the strength and durability of materials.

## What factors affect shear force?

The factors that affect shear force include the magnitude and direction of applied forces, the geometry and material properties of the object, and the boundary conditions.

## How can shear force be controlled or minimized?

Shear force can be controlled or minimized by using stronger and more durable materials, designing structures with proper support and reinforcement, and reducing the magnitude and direction of applied forces.

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