Calculating Moments Using the Method of Joints: A Tutorial

[chetzread]

It's right.
Your subsequent working must have had an error as your conclusion was incorrect.

Why not try again, be more careful with your algebra and see how far you get.I'm not sure what you mean by that.

If I consider the rod CB only, then my moment about B = Cy(8) =0... Then Cy =0... But in the author's working, the author found that Ay = 0
My answer is different with the authors ans

 

[billy_joule]

If I consider the rod CB only, then my moment about B = Cy(8) =0... Then Cy =0... But in the author's working, the author found that Ay = 0
My answer is different with the authors ans

You forgot to include Cx.

 

[chetzread]

You forgot to include Cx.

OK, I gt the answer... So for this type of problem which involve multiple force member, we should consider forces equilibrium in 1 force member only if we can't solve the forces using equilibrium at all 3 members ?

 

[chetzread]

I

OK, I gt the answer... So for this type of problem which involve multiple force member, we should consider forces equilibrium in 1 force member only if we can't solve the forces using equilibrium at all 3 members ?

In this case we only consider moment about B in a rod only? If we consider moment about B in 2 rods, we can't solve the question?

 

[billy_joule]

OK, I gt the answer... So for this type of problem which involve multiple force member, we should consider forces equilibrium in 1 force member only if we can't solve the forces using equilibrium at all 3 members ?

I'm not sure if there's a hard and fast rule.
Seeing the quickest and easiest approach will come with practice.
This particular problem could be solved much faster with the method of joints.

 

[chetzread]

I'm not sure if there's a hard and fast rule.
Seeing the quickest and easiest approach will come with practice.
This particular problem could be solved much faster with the method of joints.

I am not concerned about the speed of solving the question...
So, if we can't solve the question by moment about B = Cy(0.8) +Ay(0.8)
+ Cx(0.6) = 0
We have to choose to consider moment about a point in 1 force member only?

 

[chetzread]

I'm not sure if there's a hard and fast rule.
Seeing the quickest and easiest approach will come with practice.
This particular problem could be solved much faster with the method of joints.

Can you show how do you solve the question by method of joints?

 

[billy_joule]

Can you show how do you solve the question by method of joints?

Best to wait until after you've learned the method in class.