Engineering on a Bed of Nails

In a recent session of a Pratt School "Mechanics and Solids" course, Professor David Schaad and Michael Blagg, a civil and electrical engineering research and development engineer, conducted a demonstration of force per unit area using a bed of nails.

The demonstration was timed in conjunction with the Duke/Carolina Game. Schaad, wearing a UNC T-Shirt rested on the bed of nails while Blagg struck and broke the Carolina blue cinder block. With a Duke blue hammer,

Blagg built the bed of nails. Commonly seen as a carnival trick, the bed works through the concept of distribution of load.  One person standing on one nail will get stuck but one person spreading the weight over 1000 nails will feel little because each nail is not supporting much weight at all. 

The breaking of the concrete block does no damage because of the lack of tensile strength inherent in concrete and puts no extra significant force on Schaad.