[url=https://phet.colorado.edu/sims/html/masses-and-springs/latest/masses-and-springs_nl.html]https://phet.colorado.edu/sims/html/masses-and-springs/latest/masses-and-springs_nl.html[/url][br][br]Credits:[br]PhET Interactive Simulations[br]Universiteit van Colorado Boulder[br]https://phet.colorado.edu