Buoyancy Conceptual Questions

Two objects A and B have the same mass. Object A is placed in water and B in glycerin. Glycerin has a greater density than water. Both objects float in the liquids in which they are placed. Which object experiences a greater Buoyant force?

• A

• B

• Both A and B experience the same buoyant force

• Can not be answered without knowing the volume of A and B and the densities of water and glycerin

A steel cable holds a 120 kg shark tank 3 meters below the surface of saltwater. If the volume of water displaced by the shark tank is 0.1 m³, what is the tension in the cable (in N) ? Assume the density of saltwater is 1025 kg/m³. Take g = 10 m/s².

Mathematical Equivalence

ON

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NGSS.MS-PS2-2

A rectangular boat made out of concrete with a mass of 3000 kg floats on a freshwater lake (ρ=1000 kg/m³). If the bottom area of the boat is 6 m², how much (in m) of the boat is submerged?

Mathematical Equivalence

ON

You have a piece of wood (density 650 kg/m³) and a piece of steel (density 7750 kg/m³) both of identical volume. You hold both pieces completely submerged under water (density 1000 kg/m³). At the instant you let go, which object has a greater buoyant force on it?

• Wood

• Steel

• Both have the same buoyant force

• Can not be determined without knowing the exact mass of each piece

Two blocks attached to strings are at rest in a liquid, as shown. The only thing known about them is that they have the same dimensions. Which block has a greater mass?

• Block A

• Block B

• Both have the same mass since they are both at rest

• The answer can not be determined without knowing the density of the liquid.

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NGSS.MS-PS2-2

A layer of mineral oil is poured on top of a layer of ethylene glycol and a piece from a board game is placed at rest with its midpoint in line with the boundary between the two layers, as shown. The piece remains at rest because the density of the board game piece is greater than the density of mineral oil and less than the density of Ethylene Glycol. Earth, the mineral oil, and the ethylene glycol exert forces on the piece with magnitudes F_Earth, F_{Mineral Oil} , and F_{Ethylene Glycol} , respectively. Which of the following, where the dot represents the piece, correctly identifies the direction and relative magnitude of these forces?

• 
• 
• 
• 

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NGSS.MS-PS2-2

In each case the blocks are completely submerged in identical liquids in the beakers. The masses and volumes of the blocks is shown. Rank the blocks according to the Buoyant force experienced by the blocks from largest to smallest.

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NGSS.MS-PS2-5

Wood Blocks of different masses and volumes are floating in water with different loads on them. Rank the blocks according to the buoyant force on the blocks from greatest to least. The diagrams are not drawn to scale as far as the volume submerged is shown.

Blocks A and D have the same volume which is less than the volume of identically sized blocks B and C. Blocks A and B are made of steel of density 7000 kg/m³ and C and D are made of Aluminum of density 2700 kg/m³. Rank the blocks according to the buoyant force acting on them from largest to smallest.

4 blocks of mass and volume shown are submerged in water (density 1000 kg/m³) Rank the order of the tension in the strings from largest to smallest. (1 cm³ = 1cm x 1cm x 1cm = 10^-6 m³ and 1000g = 1 kg)

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NGSS.MS-PS2-2