PLEASE READ FIRST: I\'m having trouble setting this problem up, you don\'t need
ID: 1968447 • Letter: P
Question
PLEASE READ FIRST: I'm having trouble setting this problem up, you don't need to do the calculations, just please help me understand how to set this problem up. For instance, when looking at joint A I understand that sum f_x and f_y=0, but how do I know when to say fab is cos or sin? Also, How do I determine the angles to use for joint e and other joints if you need to use angles? If you could please walk me thourgh setting up this problem and determing the angles I would greatly appreciate it. Again, don't worry about the calculations, I just need help setting this up so I can have a better understanding.
IF YOU JUST ANSWER AND DON'T READ THE ABOVE STATEMENT I WON'T RATE, THANK YOU
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Question: Determine the force in in each member of the truss and state if the members are in tension or compression. Assume each joint as a pin. Set P=4kN.
PLEASE READ FIRST: I'm having trouble setting this problem up, you don't need to do the calculations, just please help me understand how to set this problem up. For instance, when looking at joint A I understand that sum f_x and f_y=0, but how do I know when to say fab is cos or sin? Also, How do I determine the angles to use for joint e and other joints if you need to use angles? If you could please walk me thourgh setting up this problem and determing the angles I would greatly appreciate it. Again, don't worry about the calculations, I just need help setting this up so I can have a better understanding. IF YOU JUST ANSWER AND DON'T READ THE ABOVE STATEMENT I WON'T RATE, THANK YOU ---------------------------------------------------------------------------------------------------------------------------------- Question: Determine the force in in each member of the truss and state if the members are in tension or compression. Assume each joint as a pin. Set P=4kN.Explanation / Answer
O.K. 99% of the time the first thing you're going to do when analyzing a truss is to solve for the reactions where the body is attached to the ground(or wall). Look at point C first. If the rigid body is not going to rotate about point C there needs to be a reaction at D opposing moment created by the external forces at A and B
(p)(8m) +(2p)(4m)+Dx(4m)=0
Now you have the horizontal component of member DE
Next I would solve for the vertical force at point C. The truss isn't moving and since point C is the only place offering verticle support it must be equal and opposite to the applied Forces
0=p+2p+p+Cy
You can get the horizontal reaction at C by setting it equal to the reaction at D and realizing that they need to be in opposite directions in order for the body to stay still.
Solve for the horizontal component of DE by looking at D
Don't worry about finding the angle just think back to the basic definitions of sin and cos. If you look at the straight line created by AED you see that it moves up 4 and over 8 This means that the multiplying factor for the x component would be 8 over the hypotenuse.
Dx+DEx=0=DE(8/(82+42))+Dx
You know that the reaction at D is pointed into the truss, so that is going to make DE in compression.
Since point D is on a roller the Force in member CD must be equal to the verticle reaction at C
Cy+CD=0
Since the force at C is up and DE is in compression you should be able to visualize that that would put CD in tension.
Once you have CD look back at point C you now have enough information to solve for the verticle component of CE make sure to include the Verticle reaction at C the force from member CD and the applied force P
Basically just keep doing this, working your way from right to left.
When you get to member BE it's actually way easier than it looks just draw a Free body diagram of point B don't forget that BE can only have vertical force because it's a vertical member.
On member AB you don't need to worry about sin or cos, because it only has a horizontal component.
Let me know if you need more help with this, I'm always happy to follow up.
BTW for point E notice that it's half way between the bottom and the top and halfway between the sides (hopefully that's enough of a hint to get EC)
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