A load W=2 kN is applied vertically to joint C of truss ABCDE as indicated. You will use the method of joints to obtain the axial forces in the bars and reactions at the supports A, E .

We start with the classification of the degrees of freedom as "free" or "constrained".

From the geometry of the truss, we see that we have:

Free DOF x and y at B, C, and D.

Constrained DOF x and y at A and E .

Question 1: Use MATLAB to find the axial forces in the bar.

Order the vector {X} of unknown axial forces in the bars as:

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sorry, now can you please help me or not, I finished 27 out of 29 questions, this is the problem I am stuck on and don't understand

I don't know physics ... but I know you must wait for a physics teacher to come online. Posting under PLEASE REPLY will get you nowhere.

Thanks gluglu!

To use the method of joints and find the axial forces in the bars of the truss, we can follow these steps:

Step 1: Identify the free and constrained degrees of freedom.
- From the given geometry, we see that joints B, C, and D have both x and y degrees of freedom free.
- Joints A and E have both x and y degrees of freedom constrained.

Step 2: Analyze joint C to determine the forces in the bars connected to it.
- At joint C, we have four forces acting: the applied load W (2 kN) vertically downwards, the force in bar CB, the force in bar CD, and the reaction force at joint A.
- Since the x and y degrees of freedom at C are free, the forces in bar CB and bar CD can be resolved into their x and y components, denoted as CBx, CBy, CDx, and CDy, respectively.

Step 3: Apply equilibrium equations to joint C.
- In the x-direction, the sum of the horizontal forces is equal to zero.
- CBx + CDx = 0

- In the y-direction, the sum of the vertical forces is equal to zero.
- CBy - W + CDy = 0

Step 4: Solve the system of equations to find the forces in the bars.
- Now, you can solve the system of equations to determine the values of CBx, CBy, CDx, and CDy.
- MATLAB can be used to solve this system of equations using the backslash operator (\).

Question 1: Ordering the vector of unknown axial forces in the bars.
- The vector {X} for the unknown axial forces in the bars can be ordered by listing the forces in each bar sequentially.
- For example, if we have 4 bars in the truss (AB, BC, CD, DE), the vector {X} would be:
- {X} = [F_AB, F_BC, F_CD, F_DE]

So, to obtain the axial forces in the bars and reactions at supports A and E using MATLAB, you need to follow these steps:

1. Identify the free and constrained degrees of freedom.
2. Analyze each joint of the truss using the method of joints.
3. Apply equilibrium equations to each joint and solve the system of equations.
4. Use MATLAB to solve the system of equations and obtain the values of the unknown forces.
5. Order the vector {X} of unknown axial forces in the bars as described above.