Is the net torque changed when a partner on a seesaw stands or hangs from her end instead of sitting? Is the net torque changed when a partner on a seesaw stands or hangs from her end instead of sitting? (Does the weight or the lever arm change?)

 A: No, if one simply hangs or stands, the force on the lever arm does not change. As, torque stands for $F \times r$. Here, if the only affecting force is weight,  then $F=mg$, (In case one tries to climb up the arm or jumps on it includes some extra forces.) and is directed straight down, as long as the lever arm is horizontal. If the person doesn't change his position,  namely the $r$, the torque cannot change.
A: There is a slight difference due to the change in the lever arm between the hanging position indicated and a sitting position. the girl’s weight is applied to the very end of the see-saw plank; her center of mass will be directly below where she is holding the plank.  When she’s sitting on the plank the effective lever arm will be shortened by something like 10cm.  Your center of mass is, roughly, in the middle of your body behind your navel.  If you consider where that point is for the boy in the figure you can see that it is a bit away from the very end of the plank.
A: It does not matter how the weight is arranged, as long as it's center of mass (the midpoint of weight) stays the same distance from the pivot point. Moving farther from the pivot point increases leverage, moving closer decreases leverage. Of coarse putting your feet on the ground will lessen the weight on the see saw.
