2. What is Buoyancy? Buoy = float (in Latin) Archimedes discovered this with the golden crown.

4. What is Buoyancy? Buoyancy= “the floating force” Water is “heavier” than the object…so the object floats Low density-more likely to float

5. What are the units for Buoyancy? Buoyant force is measured in Newtons (N)

6. What is displacement? Displace = push away The amount of water displaced by an object tells you the volume of that object. The weight of the displaced water is the buoyant force acting on that object.

7. How much fluid was displaced here?

8. What is buoyant force? Buoyant force is the upward force of a fluid on an object.

9. What is a fluid? A fluid is any liquid or gas.

10. What are the types of buoyancy? Positive buoyancy: Buoyant force is greater than weight so the object floats. Neutral buoyancy: Buoyant force is equal to weight so the object is suspended in the fluid. Negative buoyancy: Buoyant force is less than weight so the object sinks.

12. When does an object FLOAT? An object will float if the buoyant force is greater than or equal to the weight of object. WEIGHT BUOYANT FORCE

13. When will an object SINK? An object will sink if the buoyant force of the object is less than than the weight of the object. WEIGHT BUOYANT FORCE

14. How do you Calculate B F ? Buoyant Force= Weight of displaced fluid OR B F = W air - W water Buoyant = Weight of - Weight of object Force object in air in water

16. Buoyant Force = Weight of Displaced water When the object is submerged in water, it displaces an amount of water that weighs 3 lbs. Therefore the buoyant force pushing up on the object is 6 cm 3

17. Buoyant Force = Weight of object in air minus weight of object in water W air = 7 lbs W water = 4 lbs Buoyant Force = 7-4 = 3 lbs Volume of object=Volume of displaced water 6 cm 3

18. Challenge! If we drop this object in the water will it sink or float? Hint: compare the object’s weight in air and the buoyant force 6 cm 3

19. Challenge! If we drop this object in the water will it sink or float? Hint: compare the object’s weight in air and the buoyant force SINK 6 cm 3 7 lbs 3 lbs

20. Why do things float? 1. Things float if they are less dense than the fluid they are in. 2. Things float if they weigh less than the buoyant force pushing up on them. 3. Things float if they are shaped so their weight is spread out.

21. Hot air balloons: heat to go up Submarines: fill tanks with air to surface fill with water to submerge

22. Lowest Mass, Lowest Density, Floats Low Mass, Low Density, Neutral High Mass, High Density, Sink Sub’s carry compressed air tanks to re-fill their ballast tanks Ballast tanks Density

23. Air Density= 0.04 g/ml Balloon Density = 0.045 g/ml SINK Density

24. Air Density= 0.04 g/ml Balloon Density = 0.040 g/ml NOT MOVING UP OR DOWN Density

25. Air Density= 0.04 g/ml Balloon Density = 0.035 g/ml FLOAT

26. Shape How can you get 5000 pounds of solid steel to float?

27. Ouch! You know the Buoyant Force.

28. Output A rock has a mass of 76 g and displaced 80 mL of water when it was submerged. What is the volume of the rock? If it displaced a volume of 80mL, then the volume of the rock is 80mL!

29. OUTPUT A volume of 200 mL of water is displaced by a ducky that weighs 10N. The weight of the displaced water is 20N. What is the buoyant force on the ducky and will it sink or float? B F = 20N The ducky will float because 20N (weight of the displaced fluid) is greater than 10N (weight of the duck).

30. OUTPUT A little 27g fish displaced a volume of water that weighed 25N. The weight of the fish was 30N. What is the buoyant force on the fish and will it sink or float? B F = 25N The fish will sink because the weight of the fish is greater than the buoyant force.

31. OUTPUT A person weighs 250N while swimming in the dead sea. When outside of the water they weigh 600N. What is the buoyant force acting on them? Will they sink or float? B F = W air – W water = 600 – 250 = 350N The person will float because their weight in the water is less than the buoyant force.

32. OUTPUT A dog jumps into a pool. The water holds him up because he only weighs 10N in water. On land, he weighs 45N. What is the buoyant force? B F = 35N

33. Output An object has a weight of 7N in air. The object displaces 16 mL of water that weighs 7N. What is the buoyant force? Will the object sink or float? The weight of the displaced fluid is the buoyant force, so the B F = 7N. The object will be neutrally buoyant and float.

34. Observation Time!

37. Don’t forget your conclusion: