1. Children’s Engineering
Bringing
Children’s Engineering
to the Elementary Classrooms
Unit #6
Boats and Buoyancy
Created by Miss Kelley Davis
Page County Public Schools Division-Wide STEM Coach

2. Boats & Buoyancy
and...

3. 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

4. Say what???

5. Let me explain

6. 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.

7. 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.

8. 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.

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

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

11. 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)

13. 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!!!

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

15. 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!!!

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

17. 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.

18. 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!!!)

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

20. barge
canoe
carrier
catamaran

21. clipper
cruise liner
dinghy
dredger

22. ferry
freighter
gondola
houseboat

23. hovercraft
ironclad
kayak
life boats

24. long ship
motor boat
oil tanker
paddle boat

25. pontoon
raft
raft
row boat

26. sailboat
steam boat
submarine
trawler

27. trireme or galley
tug boat
whaler
yacht

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