Tuesday/Thursday Group Exam 2

Little Tommy Tuppin required seven stitches in his lip after he was struck in the face by a rogue tetherball. The wire constraining the tetherball snapped after drunken college senior Petey Paulsen recklessly punched the children's tetherball with too much force. Distraught, the Tuppin family has threatened to press charges, unless Petey manages to redesign the tetherball mechanism, to assure that it never snaps and no more innocent, harmless children are stuck by the ball ever again. Petey has asked you for some help in redesigning the tetherball mechanism. He has picked out a strong replacement for the wire, which has a diameter of 0.02cm, and the following stress-strain relationship:

Your task is to prove (in court, if need be) that the new wire is safe from snapping, even from an adult's tetherbal-punch force. Petey says that in order for the argument to be persuasive, you must account for the impulse associated with a tetherball serve, the threshold of tension force in the wire, and the angle of the wire from the vertical pole that the ball curves around.

A good solution is not just equations and numeric predictions, but will include commentary and discussion of those equations and predictions and reflections on what those predictions mean. We encourage you to use the simplest model that correctly captures the essential physics.