|MadSci Network: Physics|
I'm not absolutely positive that I have the exact answer that you are looking for, but I do have an answer. The feat I will describe is found in the book Invitations to Science Inquiry by Tik L. Liem (Science Inquiry Enterprises, Chino Hills, California, 1987 [2nd edition]). It is found on page 326 of the 2nd edition (event number 13.10).
Here's what to do: Have a person stand 2 foot-lengths away from a wall, facing the wall. (A "foot length" is the length of that particular person's foot, with shoes on.) The person is to bend over at the hips and let his/ her head lean against the wall. Another person hands the first person a straight-back chair (with the chair's back toward the wall), and the first person is to lift the chair, keeping his/her head against the wall. With the chair in the lifted position, the person is to straighten up. Most females can do it, but most males can not.
Tik L. Liem explains that it is due to the differences in the center of gravity of males versus females, and also that males usually have longer feet than females. The male's center of gravity with the chair is out beyond his toes, while the female's center of gravity is above her foot.
John Link, MadSci Physicist
Try the links in the MadSci Library for more information on Physics.