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

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

1. ### SteveGuest

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.