Momentum And Rocket Propulsion

Description
A basket ball and a tennis ball kept in contact ,held at a hight is allowed to fall and hits the ground. What will be the nature of motion of the tennis ball after the impact? The result is there in the presentation but you have to find the reason.The lecture extends to discussion of rocket propulsion.

Prof. Walter Lewin, 8.01. Classical Mechanics, Massachusetts Institute of Technology: MIT OpenCourseWare), http://ocw.mit.edu (Accessed June 10, 2011). License: Creative Commons BY-NC-SA: http://ocw.mit.edu/terms/#cc