# Forces in a staically determinate cantilever Truss, why some experiences compression while...

Discussion in 'Physics' started by Steve, Oct 8, 2018.

1. The Redundant Truss Apparatus is constructed with units of basic triangular pin-jointed.

At joint 1, it is fixed firmly due to a support.

At joint 2, it is fixed to a movable support.

Suppose at joint 4, $F = 250N$

Q1) Using pin-jointed Theory, show the full working to calculate theoretical member forces for the framework.

For qn1, I am able to obtain the magnitude of the forces for each members using free body diagrams. A small part of my calculation based on free-body diagram is at joint 4 $$\frac{1}{\sqrt2}F_7 - F = 0$$ $$F_7 = 250\sqrt2 N$$

Q2) From your results and the theoretical member forces, identify which members are in compression and which are in tension. Explain your choices.

Even if I answer qns 1 correctly, I have no idea how to explain why some of them experience compression while some experience tension.

Q3) Explain the reading of member 5.

While I understand that member 5 does not apply any force, I have no idea how to explain it.