What is the relationship between buoyancy and the weight of displaced water? Archimedes’ Principle states that buoyancy is equal to the weight of the water displaced by the object.

Why is the loss of weight of the object in a liquid only an apparent loss of weight? When the object is put in water it looks like it has lost weight however the weight is just being supported by the buoyant force of the water and will return when the object is back in air.

How did the apparent loss of weight compare with the weight of water displaced for each object? The apparent loss of weight should be equal to the weight of water displaced by the object because weight of water displaced is buoyant force (Archimedes’ principle) and how much weight is “lost” is equal to how much is being pushed up.

If an object floats in a liquid, how does the loss of weight compare with the weight of the object in air? If the object floats then it loses all its weight so the loss of weight will equal the weight of the object in air.

Does the buoyancy of a liquid change as the mass of the object changes? As the mass increased the buoyancy increased when the object was floating but when the object sank the mass increased and the buoyancy stayed the same.

Do all liquids have the same buoyancy? No, all liquids do not have the same buoyancy. Looking at the results for 12 pennies, the buoyancy is greatest in the saltwater and least in the rubbing alcohol. The less dense the liquid the smaller the buoyant force.

Compare the weight of the object in air to the weight of the displaced water when the object floated. When the object floats the weight of the object in air is equal to the buoyancy and since buoyancy is equal to the weight of the displaced water (Archimedes’ Principle), the weight of the object in air is equal to the weight of the displaced water.

Compare the weight of the object in air to the weight of the displaced water when the object sank. When an object sinks the weight of the object in air is greater than the buoyancy and since buoyancy is equal to the weight of the water displaced (Archimedes’ principle), the weight of the object in air is greater than the weight of the displaced water.

1. What is the buoyant force from the fluid on the object? Weight of object in air = 32.0 N Weight of object in fluid = 10.0 N Will the object float or sink?

2. What is the weight of the object in air? Buoyant force = 17. N Weight of object in fluid = 0 N Will the object float or sink?

3. What is the buoyant force on the object? Mass of displaced water = 408. g Weight of object in air = 5.2 N Will the object float or sink?

4. What is the weight of the object in the fluid? Buoyant force of the fluid on the object = 25. N Mass of object = 4.5 kg Will the object float or sink?

5. When placed in water which will displace more fluid? Buoyant force = 12. N Buoyant force = 20. N 6. When placed in water will the objects float or sink? Mass of object = 1.22 kg Mass of object = 3.51 kg Object 1Object 2

7. Which has a better chance of floating? Why? 50g

8. On a cloudy day, a sealed packet of potato chips is taken to the top of a mountain. The packet is found to be blown up like a balloon because A.the air outside the packet is hotter than the air inside the packet. B.the air outside is now at a lower pressure than the air inside the packet. C.the ultraviolet radiation has increased. D.the packet has a small hole that allowed air to leak in.

9. A lady weighs 500 N and wears stiletto shoes. The area of the stiletto heel is m 2. The pressure the lady exerts by standing on one stiletto heel is A. 200 N/m 2 B.5000 N/m 2 C N/m 2 D N/m 2

10. Archimedes’ principle says that an object is buoyed up by a force that is equal to the A.volume of the fluid displaced B.mass of the fluid displaced C.weight of the fluid displaced D.mass of the object E.None of the above

11. Where is the buoyant force on a submerged rock greater, near the surface of the fluid or 10 m below the surface? A.near the surface B.10 m below the surface C.neither place – the buoyant force is independent of depth

12. The buoyant force on an object is least when the object is A.submerged near the surface B.partly submerged C.submerged near the bottom D.None of the above

13. The reason a life jacket helps you float is that A.the jacket has the same density as an average human B.the jacket repels water C.the jacket makes you weigh less D.the jacket enables you to displace more water

14. The reason an iron ship doesn’t sink is that A.air inside decreases it’s weight B.the iron ship displaces more water than it would if it were in a solid block C.iron is less dense than water D.Nonsense – an iron ship will always sink

15. When first put in water, a plastic toy boat will sink until A.it displaces a volume of water equal to its own volume B.the water density equals the density of the boat C.it displaces a weight of water equal to its own weight D.the buoyant force equals the volume of the boat E.the buoyant force equals the density of the boat

16. Two equal-sized buckets are filled to the top with water. One of the buckets has a piece of wood floating in it, making its total weight A.more than the weight of the other bucket B.less than the weight of the other bucket C.equal to the weight of the other bucket

17. A block of balsa wood floats on water while a same-size block of lead lies submerged in the water. The buoyant force is A.greater on the wood B.greater on the lead C.the same for both

18. A kilogram of lead and a kilogram of aluminum are submerged in water (aluminum is less dense than lead). The buoyant force is A.greater on the aluminum B.greater on the lead C.the same on each D.impossible to determine

19. A boat loaded with a barrel of water floats in a swimming pool. When the water in the barrel is poured overboard, the swimming pool level will A.fall B.rise C.remain unchanged D.impossible to determine

20. When a boat sails from fresh water to salt water, the boat will float A.higher in the salt water B.lower in the salt water C.at the same level

21. If the part of an iceberg that extends above the water were removed, the A.density of the iceberg would change B.buoyant force on the iceberg would decrease C.iceberg would sink D.pressure on the bottom of the iceberg would increase E.None of the above

22. When you float in salt water compared to floating in fresh water, the buoyant force that supports you is A.the same B.greater C.less

23. Suppose a stone weighs 3 N in the air but in water it weighs only 2 N. What is the buoyant force acting on the stone? A.2 N B.4 N C.5 N D.3 N E.1 N

24. The volume of water displaced by a floating N boat A.is the volume of N of water B.is the volume of the boat C.depends on the shape of the ship’s hull D.is cubic meters

25. A block of wood of mass 3.5 kg floats in water. Calculate the buoyant force on the block

Answers 1)22.0 N; sink 2)17. N; float 3)4.00 N; sink 4)19. N; sink 5)object 2 6)object 1 will float; object 2 will sink 7)larger object because it will displace more water which means it will have a bigger buoyancy

Answers 8)B 9)D 10) C 11) C 12) B 13) D 14) B 15) C 16)C 17)B 18) A 19) C 20) A 21) B 22) A 23) E 24) A 25) 34. N