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Counting cracks in glass gives speed of projectile

Simple relationship between velocity and number of spokes in star-shaped fracture

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A shattered windshield has a story to tell. The key to hearing it is counting the cracks.

The number of cracks that emerge in a plate of glass or Plexiglas relates to the speed of the object that broke it, researchers demonstrate April 26 in Physical Review Letters. This simple relationship could prove useful for forensic scientists, archaeologists and even astronomers.

Over the past century, most research into cracks has focused on parameters that determine whether a material remains intact when struck.

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