Two blocks with mass m1,m2 connected by a spring with spring constant k2.
Drag "hand" in the simulation to push or pull the system (with spring k1) and watch how the system moves.
Click [url=http://www.phy.ntnu.edu.tw/ntnujava/javaswf/box2pull.swf]Usage link[/url] at the bottom of the simulation for illustration with flash movie.

Virtual Physics laboratory Original URL

Fu-Kwun Hwang, Dept. Of Physics, National Taiwan Normal University.