Noticing how much the G3 scientists love putting on their ‘creative thinking caps,’ I thought it was about time to learn about buoyancy and to play with that concept. Not only is it a fun concept to explore, but it allowed us to have giant tubs of water in the room to play with 🙂
When people talk about buoyancy, inevitably there is mention of Archimedes’ Principle. Archimedes (born 287 BC; died 212 BC) was a famous Greek mathematician who, among other things, is well known for his study of buoyancy. [He was also famous for running through the streets naked after a great discovery screaming, “Eureka!”] His Principle states: Any floating object displaces its own weight of fluid.
All of us have experienced this Principle in action. For example, have you ever noticed that when you get in the bathtub, the water level rises, sometimes even spilling over the top to make room for your body? But how does an object – especially a large object like a cruise ship (or the Titanic even!) float in the water? The reason a boat (or another object) floats in fluid is thanks to something called “buoyant force.” Gravity – a force we are well familiar with – pushes down on an object. However, if an object is able to displace enough water and to create a volume/size large enough to compensate for its own weight, there will be enough of a buoyant force pushing the object UP in the fluid…and that’s why an object can float. Our G3 scientists actually watched a nifty student video about buoyancy on youtube uploaded by user Nroo:
Once the video was completed, the G3 crew watched a brief demonstration by Nicole about buoyancy. We had a small tub of water, and two identical blobs of play dough. When the first hunk of play dough was rolled into a ball shape and put into the tub of water, what do you think happened? As most of our scientists guessed, it sunk to the bottom of the tub. Why? There was not enough volume/surface area to create the appropriate amount of buoyant force to float the play dough. The second hunk of play dough was shaped into a simple boat (even though there were requests for a play dough boat that looked like the Titanic). Can you guess what happened when we put the ‘boat’ into the tub of water? It floated!
Now for the real test of the day. Using an experiment outlined by PBS’s FETCH program (“Float My Boat“) as the basis for our own experiment, each G3 scientist was initially given a 6” square of tin foil and told to design a simple boat with just that material. There were no other instructions – any design would do. When the boat was ready, each G3 scientist was instructed to carry their simple boat over to a large container of water to test it out and see just how many pennies it could hold. [It should be noted that Nicole had obtained a box of 2,500 pennies for use during the program and most members of our crew were in awe of how heavy a box of 2,500 pennies can be…everyone wanted to flex their impressive muscles.] Boats created throughout the afternoon held anywhere from 1 to an awesome 559 pennies! Some scientists chose to use multiple sheets of tin foil. Some opted for wide, flat boats while others built long boats with tall sides. In the show-and-tell at the end of our program, several scientists shared their designs with us. Among them were the self-named “Bird’s Nest” aka “Catcher’s mit”; S. S. Colossal; “Beef Burrito”; and the crowd pleasing “Weiner.”As a treat, each scientist got to take home not only their boats but a super cool rubber duckie 🙂 I can’t wait to see what we’ll be learning about next!…