Museum of Science and Industry

Interactive, hands-on activities will be a key part of Science Storms as guests explore physics and chemistry like never before. Guests will conduct the Museum version of an actual experiment on forces in granular materials used by Dr. Robert Behringer at Duke University. Scientists use experiments like these to see gravity and friction in action.

Guests Will:

• Turn a container to change the force on disks made of a special material that shows stress points when lit with polarized light.
  
  
• Notice areas where the disks are under the greatest stress and where they are not stressed at all.
  
  
• Use a wand to move a magnet and exert an extra force on the disks. Observe how the stress patterns change with the added force.

Spotlight on Stress
These disks are made of a special material that shows stress points when lit with polarized light. The stress points are created by the forces of gravity and friction. Gravity pulls the disks downward, causing them to exert a force on the disks below them. Friction occurs when the disks rub against each other.

Scientists are still learning about how the forces of gravity and friction travel through materials.
Studying forces in granular materials will give us a better understanding of how piled grains can cause a silo to burst or how the Earth splits along the San Andreas Fault. Guests will see from this experiment that forces do not move through granular materials in a straight line.