I am looking at the solution my teacher posted, in order to find Mo, he broke it

Question

I am looking at the solution my teacher posted, in order to find Mo, he broke it up into Mx, My, and Mz. his answers are as such:

Mx= 2(.8)-5(.4)= -.4 kN*m

i understand this because the 2 kN force turns it clockwise (positive) and the 5 kN force turns it counter clockwise (negative) but once we get to My and Mz, i dont know why some moments are negative and other aren't

My= -5(.8)= -4 kN*m

Mz= -1(.8)+3(.8)+3(.8)= 4 kN*m

I know where all the number are coming from but i still dont know why things like My are negative even though it is being rotated clockwise around the y axis, so shouldn

The horizontal top of a concrete column is subjected to the system of forces shown. Represent the resultant of all forces as a force R at point O and a couple M. Also specify the magnitudes of R and M. Problem 2/161

Explanation / Answer

1.) apply right hande thumb rule ---> check in which direction moment is acting because of a force.

example :My= -5(.8) // because moment direction is -y.... not +y

and similarly in

Mz= -1(.8)+3(.8)+3(.8) // moment of 1kN force is acting in -Z direction while other's in +Z and so the net moment is given value.

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