Here is the video of the “Buoyancy: Throwing rocks from boats (and weighing coins)” demonstration. The two GIFs show the dropping of the coins into the cup and then the dumping of them into the water. The full video is linked here.
Dropping the coins into the cup showing that 9 quarters displaces 50 ml of water.
Dumping the coins out showing that, when submerged, they displace a lot less than 50 ml.
An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (email@example.com). I also welcome comments (through the comments section or via email) on improving the demonstrations.