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# Physics/Mechanics

Question
Hi Steve.

Season's Greetings!!!

There is this experiment called the 2 finger lift..can be viewed on Youtube. Basically 4 persons attempts to lift a 5th person using only 2 fingers. The 5th person sits on a chair and the other 4 each inserts 2 fingers on 4 locations...under each arm pit and under each knee.The 1st attempt fails. The group then chants an incantation and repeats the experiment..and presto it works! I know its a trick..so I did it with my kids and their friends and it works exactly as it was shown on Youtube..how come?? Thanks

This is a trick and a simple demonstration of vectors.  If the person keeps their body rigid, then the force can be directed all upwards.  If they go limp, the force has to pull the shoulders away from the knees as well as to lift vertically, reducing the upward component of force by somewhere in the 40-50% range or more.  The incantation is pure show.  Since approximately 75-80% of a person's body mass is in their torso and thighs, the effect is probably even more pronounced for this case, and extra tension in the torso to keep it rigid would cause a large change in the necessary lifting force.  If they didn't know it was happening, then I'd blame the power of suggestion and them subconsciously playing along.

Presto!

Physics

Volunteer

#### Dr. Stephen O. Nelson

##### Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

##### Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.