8.1 Fluids and Buoyant Force

Which of the following is a fluid at room temperature?

• oil

• wood

• lead

• aluminum

Which of the following statements is correct?

• Liquids have a definite shape.

• Gases have a definite volume.

• Gases have a definite shape.

• Liquids have a definite volume.

What is true about the volume of displaced fluid for an object that is completely submerged?

• The volume of displaced fluid is equal to the object’s volume.

• The volume of displaced fluid is less than the object’s volume.

• The volume of displaced fluid is greater than the object’s volume.

• The volume of displaced fluid is not related to the object’s volume.

If an object weighing 50.0 N displaces a volume of water with a weight of 10.0 N, what is the buoyant force on the object?

• 60.0 N

• 50.0 N

• 40.0 N

• 10.0 N

Which of the following statements is true about the buoyant force on an object that is floating on the surface of a lake?

• The buoyant force is greater than the weight of the object.

• The buoyant force is equal to the weight of the fluid displaced.

• The buoyant force is the same as when the object is completely submerged.

• The buoyant force is less than the density of the water.

In which of the following situations will an object sink?

• The mass density of the object is less than the mass density of the fluid.

• The buoyant force on the object is equal to the weight of the object.

• The mass density of the fluid is less than the mass density of the object.

• The weight of the fluid displaced equals the weight of the object.

An uncooked egg sinks in fresh water but floats in salt water. Which of the following expressions about the egg’s density (ρ_egg) with respect to the density of fresh water (ρ_fw) and the density of salt water (ρ_sw) is correct?

• ρ_egg < ρ_fw < ρ_sw

• ρ_sw < ρ_egg < ρ_fw

• ρ_fw < ρ_egg < ρ_sw

• ρ_fw < ρ_sw < ρ_egg

Which statement about an object placed in water is correct?

• The apparent weight is always less than the weight of the object in air.

• The apparent weight is always equal to the weight of the fluid displaced.

• The apparent weight is never equal to zero.

• The apparent weight is never greater than the buoyant force.

What is true about water as ice being not a fluid but water as liquid or steam being a fluid?

• water as liquid or steam can flow and change shape.

• water as a liquid and gase has a definite volume

• water as solid can flow and change shape.

• water as a liquid and gase has a definite shape.

Calculate the buoyant force on a cube of metal with an edge of 1.3 cm that is placed in salt water. The density of the metal is 7.86 x 10³ kg/m³, and the density of the salt water is 1.025 x 10³ kg/m³.

• 1.3 x 10^-2 N

• 1.69 x 10^-1 N

• 2.2 x 10^-2 N

• 2.2 x 10⁴ N