mechanics? (Find equation that represents moment balance at point A. Assume pos. moment is counterclockwise.)

[Leons]

can someone explain how to find the equation that represents the moment balance at point A. Assume the positive moment is counterclockwise.
or maybe someone could tell which one i have to find first ?

 

[khansaheb]

can someone explain how to find the equation that represents the moment balance at point A. Assume the positive moment is counterclockwise.
or maybe someone could tell which one i have to find first ?View attachment 35637

Assume that the given FBD is correct. Assume that the the force is applied at point T.

Draw a vector TA from T to point A. Assume that the vector is r . Determine r X T (vector cross-product)

continue...

 

[MaxMath]

Only T and the 100Nm have non-zero moments about A. Decompose T into horizontal and vertical components the modes of which will be 3/5 |T| and 4/5 |T|, respectively. Then it’s straightforward. Just be careful with the signs.

By the way, to find the moment balance equation, we must assume the system is in balance, i.e., is static.