Newton's Cradle is a device that demonstrates the concept of conservation of motion. If there was no air resistance on earth, the balls on the end of the line would keep going back and forth forever. Since we have air resistance on earth the device will eventually come to a stop. A student decides to see how many hits it would take in order for the device to stop moving.

The student records the first hit having a height as being 20 cm. The student records the second hit having a height as being 19.6 cm. The student records the third hit having a height as being 19.2 cm.

How many hits would it take for the balls to stop moving? SHOW ALL WORK!!!