Kamien, Randall DAmbroso, M. ADurian, Douglas J2023-05-232023-05-232005-10-012017-10-10https://repository.upenn.edu/handle/20.500.14332/43347We present data for the time dependence of wooden spheres penetrating into a loose noncohesive packing of glass beads. The stopping time is a factor of 3 longer than the time d ∕ v0 needed to travel the total penetration distance d at the impact speed v0. The acceleration decreases monotonically throughout the impact. These kinematics are modeled by a position- and velocity-dependent stopping force that is constrained to reproduce prior observations for the scaling of the penetration depth with the total drop distance.© 2005 American Physical Society. You can view the original article at: https://journals.aps.org/pre/abstract/10.1103/PhysRevE.72.041305Physical Sciences and MathematicsPhysicsArticle