Simple Equivalence Problem- help please (First Year Statics)

In summary, The conversation discusses a problem with finding the correct location of the intersection of two forces, F1 and F2, given their magnitudes and a moment. The correct answer is given as x = 2.34, but the person asking the question initially got a different answer. The mentor explains that the line of action of the resultant force must also be considered in finding the correct answer, and suggests finding the sum of moments and using that to find the line of action of the resultant force. The person asking the question later figures out their mistake and gets the correct answer.
  • #1
lc99
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Okay, so i am having severe problems with figuring out what i did wrong...
I am given : F1 = 250 and F2 = 90
The correct Force result is = 245 i +228 j with magnitude of 335 .
The moment given is 500 lb*ft.

I am trying to find the result's line of action that would intersect member BC measured from B. The correct answer is x = 2.34.

But, i got some other answer. I found the location of intersection with M = Fy * x (Fy because Fx would be 0 along the x-axis).

so , 500 = 228*x --> x = 2.19?? Which is wrong :(
 

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  • #2
lc99 said:
The correct Force result is = 245 i +228 j with magnitude of 335 .
Ok, but that also has, of itself, a line of action. It would pass through the point of intersection of the lines of action of F1 and F2. You have not factored this in.
The safer approach is to pick an axis and find the sum of miments about it from the applied forces. Then find the line of action of the resuktant that yields the same moment.
 
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  • #3
haruspex said:
Ok, but that also has, of itself, a line of action. It would pass through the point of intersection of the lines of action of F1 and F2. You have not factored this in.
The safer approach is to pick an axis and find the sum of miments about it from the applied forces. Then find the line of action of the resuktant that yields the same moment.
Thanks! I figured out that i didn't add up all the moments
 

Related to Simple Equivalence Problem- help please (First Year Statics)

1. What is a simple equivalence problem in first year statics?

A simple equivalence problem in first year statics involves comparing two systems or structures to determine if they are equivalent in terms of their forces and moments. This is often done by drawing free body diagrams and applying the equations of equilibrium.

2. How do you solve a simple equivalence problem?

To solve a simple equivalence problem, you first need to draw free body diagrams of the two systems or structures being compared. Then, apply the equations of equilibrium (sum of forces and sum of moments) to determine if the forces and moments are equivalent. If they are, the systems are considered equivalent.

3. What is the importance of solving simple equivalence problems in first year statics?

Solving simple equivalence problems in first year statics helps to develop an understanding of the principles of equilibrium and how different systems or structures can have equivalent forces and moments. This is important in engineering and other scientific fields where understanding and manipulating forces is crucial.

4. What are some common mistakes made when solving simple equivalence problems?

Some common mistakes made when solving simple equivalence problems include not drawing accurate free body diagrams, misapplying the equations of equilibrium, and not properly considering all forces and moments acting on the system. It is important to carefully analyze the problem and double check all calculations to avoid these mistakes.

5. Can you provide an example of a simple equivalence problem and its solution?

Sure, here's an example: Two beams with the same length and cross-sectional area are connected by a pin at their midpoint. One beam is supported by a hinge at one end, while the other is supported by a roller at the other end. The question is: are the forces and moments acting on the two beams equivalent?

To solve this, we draw free body diagrams of both beams and apply the equations of equilibrium. We find that the forces are equivalent, but the moments are not. This is because the hinge support prevents the beam from rotating, while the roller support allows for rotation. Therefore, the beams are not equivalent in terms of moments.

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