cloud1.png notes = http://openclipart.org/detail/99229/landscape-by-rg1024
DrakoonSonne.png notes = http://openclipart.org/detail/166921/drakoon-sun-by-jogdragoon
brick-tile.png notes = http://openclipart.org/detail/9523/-by--9523
barrel.png source=PhET notes=balancing act
boy-standing.png source=PhET notes=balancing act
girl-standing.png source=PhET notes=balancing act
mystery-object-01.png source=PhET notes=balancing act
trash-can.png source=PhET notes=balancing act
ollie.gif source=PhET notes=motion-series
water-bucket.png source=PhET notes=Noah