Motivated by recent experiments, we present a study of the dynamics of cracks
in thin sheets. While the equations of elasticity for thin plates are well
known, there remains the question of path selection for a propagating crack. We
invoke a generalization of the principle of local symmetry to provide a
criterion for path selection and demonstrate qualitative agreement with the
experimental findings. The nature of the singularity at the crack tip is
studied with and without the interference of nonlinear terms.Comment: 7 pages, 11 figure