Engineering Statics Question Regarding Finding Normal Force

In summary, the problem involves a pulley system with 100N of force in each cable and a beam with a 100N downward force on the right end and a normal force on the left end. After taking the moment about point B and accounting for equilibrium, the equation -100cos(30)(0.3) + Nwall (0.1) = 0 is obtained. A mistake is noticed and the final equation is adjusted to account for the perpendicular component of the normal force of the wall. This results in a final normal force of 300N. It is also noted that the direction of this force should be indicated.
  • #1
Temp0
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Homework Statement


http://i.imgur.com/rwbXqW8.png


Homework Equations





The Attempt at a Solution


So I started off by analyzing the pulley, and determined that each cable carries 100N of force. After that, I drew the FBD of the beam, where there is a 100N force going downwards on the right end and the normal force perpendicular to the beam on the left end. I took the moment about point B, and since this is in equilibrium, the moment should be zero. Therefore I came up with the equation:

-100cos(30)(0.3) + Nwall (0.1) = 0
Where Nwall is the normal force provided by the contact with the wall.
I came up with the answer 259.8N, can anyone check my work please? Thank you in advance.
 
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  • #2
Temp0 said:

Homework Statement


http://i.imgur.com/rwbXqW8.png


Homework Equations





The Attempt at a Solution


So I started off by analyzing the pulley, and determined that each cable carries 100N of force. After that, I drew the FBD of the beam, where there is a 100N force going downwards on the right end and the normal force perpendicular to the beam on the left end. I took the moment about point B, and since this is in equilibrium, the moment should be zero. Therefore I came up with the equation:

-100cos(30)(0.3) + Nwall (0.1) = 0
Where Nwall is the normal force provided by the contact with the wall.
I came up with the answer 259.8N, can anyone check my work please? Thank you in advance.
If the normal force at the left end was perpendicular to the beam, then there would be a component of that force acting parallel to the wall. But the wall is frictionless. So...?
 
  • #3
Yeah I noticed my mistake, the beam will create a contact force that's perpendicular to the wall and I need to figure out the angle for the component perpendicular to the beam where I can then take the moment.
 
  • #4
Temp0 said:
Yeah I noticed my mistake, the beam will create a contact force that's perpendicular to the wall and I need to figure out the angle for the component perpendicular to the beam where I can then take the moment.
Yes, that will work.
 
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  • #5
So, for my final equation, I found that the normal force of the wall is 30 degrees from the perpendicular component to the beam, so I have:
The sum of moments about point B = Nwall cos30 (0.1) - 100cos30(0.3) = 0
Getting an Nwall of 300.
 
  • #6
Temp0 said:
So, for my final equation, I found that the normal force of the wall is 30 degrees from the perpendicular component to the beam, so I have:
The sum of moments about point B = Nwall cos30 (0.1) - 100cos30(0.3) = 0
Getting an Nwall of 300 N .

Looks good!
I suppose you should indicate its sense...whether the force of the beam on the wall perpendicular to the wall is acting up and to the left or down and to the right... ?
 

1. What is statics in engineering?

Statics is a branch of mechanics that deals with the study of objects at rest or in constant motion. It focuses on the analysis of forces acting on objects and their effects on equilibrium.

2. What is normal force in engineering statics?

Normal force is the perpendicular force exerted by a surface on an object in contact with it. In engineering statics, it is used to determine the support or reaction forces of an object in equilibrium.

3. How do you find the normal force in a given scenario?

The normal force is equal to the weight of the object if it is on a horizontal surface. If the surface is inclined, the normal force can be calculated using trigonometric functions and the weight of the object.

4. What is the significance of normal force in engineering statics?

The normal force is an important concept in engineering statics as it helps in determining the stability and equilibrium of structures. It also plays a crucial role in calculating reaction forces in support structures.

5. How does the normal force affect the stability of an object?

The normal force acts as a counterforce to external forces acting on an object, thereby preventing it from moving or tipping over. The greater the normal force, the more stable the object will be.

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