Students construct a model of an object in orbit by balancing centripetal force, or circular force, with gravitational force. Materials Student worksheet (docx) OR view on Google Docs Straw or narrow tube (1 per group) String Small object to use as the unknown swinging mass (e.g., golf ball, eraser, tennis ball.) (1 per group) Small object to use as the known hanging mass (e.g., washers) (1 per group) Scale Stopwatches OR timer app Management Consider limiting group sizes to 3-4 to keep all stu