How Do You Calculate Forces in a Truss Without Given Angles?

[ZaZu]

Hello,

I have a test after 4 hours and I really need to know how to solve this :S
I tried my best and threw 4 pages of scratch papers already !
Please help me...
I know I am doing it wrong, I tried and tried but it did not work .. I am really frustrated I feel like I am going to fail the test -.-

The angles are not given so I have no idea how find these forces .. and the vertical force of 100Kn, how is it distributed to both sides ??!

This is all I can do until now :

http://img7.imageshack.us/img7/3943/image169g.jpg

Please help me

 

[PhanthomJay]

Probably too late for your test, but always solve for the support reactions first using the equilibrium equations; I assume one support is pinned and the other is a roller support. Then, after solving for the x and y components of the reactions at the pin, and the y component of the reaction at the roller, then look at the joints to solve for the member forces, again using the equilibrium equations. Your forces at the joints are not correct.

 

[nlightner]

.

Dear student,

I understand your frustration and I am here to help you. First of all, don't worry, you still have 4 hours and I am confident that with some guidance, you will be able to solve this problem successfully.

To find the forces on a truss, we use the method of joints and method of sections. The method of joints involves analyzing the forces at each joint in the truss, while the method of sections involves cutting the truss into sections and analyzing the forces acting on each section.

Based on the diagram you provided, it seems like you have already attempted to use the method of joints. However, it is important to note that in order to solve for the forces, you will need to know the angles at each joint. These angles can be found by using basic trigonometry and the given dimensions of the truss.

As for the vertical force of 100Kn, it is important to understand that this force is distributed equally to both sides of the truss. This means that each side will experience a force of 50Kn. This can be seen by drawing a free body diagram of the entire truss and applying the principle of equilibrium.

I suggest taking a step back and reviewing the concepts of truss analysis and the methods mentioned above. Once you have a better understanding of these concepts, you can then approach the problem with a clearer mind and hopefully solve it successfully.

Remember, don't give up and keep trying. With some practice and a better understanding of the concepts, I am sure you will be able to solve this problem and do well on your test.

Best of luck!