What direction would torque be on a trebuchet in motion

[Physics Student 1]

What direction would torque be on a trebuchet in motion at the point where the swing arm is parallel to the ground?

 

[CWatters]

The heavy counter weight produces a torque that causes the arm to rotate. If it's firing from left to right (as you look at it) then the torque on the arm is clockwise.

Note: If the arm and counter weight rotate one way (eg clockwise), then the frame and the planet it sits on rotates the other way (due to conservation of angular momentum). The amount the planet rotates will be exceptionally small but it does rotate. Just as it rotated the other way when the trebuchet was armed.