Descriptions of systems 1) A collection of objects. 2) No net force acts on the system, and no mass or energy enters or exits the system. 3) No mass enters or leaves the system, but energy can. External forces may influence the system. 4) Mass and energy may enter or leave the system, and external forces may influence the system. Record the number that correctly describes each system. Isolated System Closed Open System System System 3 1 2 4