Children’s Engineering Bringing Children’s Engineering to the Elementary Classrooms Unit #6 Boats and Buoyancy Created by Miss Kelley Davis (kdavis@pagecounty.k12.va.us) Page County Public Schools Division-Wide STEM Coach

Boats & Buoyancy and...

Did you ever wonder what makes an object float??? Wonder no more! There are 3 things that cause an object to float. displacement density buoyant force

Say what???

Let me explain

Displacement When an object is placed in the water, it “pushes” the water away. An object will float if it “displaces” the amount of water that is equal to its weight.

Density All objects are made of molecules. The molecules can be loosely packed together OR tightly packed together. An object will float if the molecules are loosely packed together.

Buoyant Force The buoyant force is the opposite of gravity. Gravity pulls an object down. The buoyant force pushes an object up. An object will float if the buoyant force is stronger than the force of gravity.

And....AIR! Don’t forget, the more air in an object, the more likely it is to float. DUH!!!!!!

Who can name some parts of a boat??? So let’s talk about boats! Who can name some parts of a boat???

Do you know where/what each part is? bow front of the boat hull main body/bottom of the boat keel bottom/centerline of the boat (backbone) port left side (when looking forward) stem forward most part/tip of the boat stern rear of the boat starboard right side (when looking forward)

Let’s look closer at the hull There are 2 kinds of hulls... Displacement Hull for those folks that like to move as fast as possible in the water...like me! Planning Hull for those folks that like to ride on top of the water...like me too!!!

There are 5 different types of hulls flat bottom vee bottom round bottom multiple bottom gull or cathedral bottom

Time for some surprising facts about boats & buoyancy from the smooth sloth Did you know it is easier to lift a heavy person when they are in the water??? It’s all because of that buoyant force pushing them up and out of the water. Steel nails sink but steel ships float...because their hulls are filled with air. Ships float higher in sea water than in fresh water because the salt makes the water more dense. Ships float higher in cold water then warm water because the cold is more dense. All those molecules slow down and stop moving when its cold!!!

Are you still wondering who that naked man on the first slide was??? Ummmm, yeah?

His name is Archimedes! He was a Greek mathematician and astronomer. One evening, when he stepped into the tub to clean his stinky body, something amazing happened! The water level in the tub rose up. He figured out that the “weight of the water displaced was equal to the buoyant force.” Without thinking, or putting on a towel, he shrieked “Eureka!” and ran through the town sharing his new knowledge.

Wow, that’s pretty cool! (He’s also the guy who discovered the value of pi...luckily, he wasn’t in the tub when that happened!!!)

Before you start designing your own boat, let’s take a look at a few different types of boats throughout history!

barge canoe carrier catamaran

clipper cruise liner dinghy dredger

ferry freighter gondola houseboat

hovercraft ironclad kayak life boats

long ship motor boat oil tanker paddle boat

pontoon raft raft row boat

sailboat steam boat submarine trawler

trireme or galley tug boat whaler yacht

And of course our favorites the pirate ship AND the float!