Hi, Ok so we were told to find our center of mass using the reaction board method, but modified. We just do a pushup position with our hands on a scale, I have a electronic one and toes on the floor. My values obitained are: weight=68kg the scale reading in a pushup position=48.9kg horizontal distance from hands to my toes=112cm http://www.geocities.com/mvxraven/pushup.JPG Locate my center of mass: Ok so, the sum of torques=(F1 x d1) + (F2 x d2) F1=reaction force from scale F2=weight force d1=112 cm d2=my unknown value! 0=(48.9 kg x 9.81)(1.12m) + [-(68kg x 9.81)(d2)] (negative because it's going clockwise) 667.08 (d2)=537.27 d2=0.805m or 80.5 cm. Alright, that means my center of mass is 80.5 cm from my toes, making it around the belly area?:uhh: Second part of the question says what happens if a 20kg backpack is placed halfeway between you hips and shoulders. I can't "do" this, I must only calculate, so can't find reaction force with scale. So anyone have ideas for this one? I think I can do the same thing? So : Sum of torque=(F1 x d1) +(F2 x d2) + (F3 x d3)? F3 being the reaction force of my back against the back pack on me. But that doesn't work, because that just means the torque force for F1 and F2 will cancel and my d3 can't be 0. So how does this work? Thanks again!