Two students stand at rest, facing each other on frictionless skates. They then start tossing a heavy ball back and forth between them. Describe their subsequent motion?

The students will move away from each other as explained by Newton’s Third Law which states that "To every action, there is an equal and opposite reaction." If the students are on frictionless skates, their action of throwing the ball will propel them in the opposite direction. Once the motion is initiated, they continue to move away from each other unless stopped by another force.