Buoyancy

An object in a fluid is buoyed up by a force ______ the weight of the fluid displaced

1 pts

volume_mute

greater than

equal to

less than

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Explanation

What is the buoyant force exerted on a cubic foot of steel by the water?

1 pts

volume_mute

Suppose a cubic foot of steel (weight: 480 lb) is below the surface of water.

What is the buoyant force exerted on it by the water?

480 lb

62.4 lb

417.6 lb

0 lb

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how much force would you have to exert to lift the steel under water?

1 pts

volume_mute

Suppose a cubic foot of steel (weight: 480 lb) is below the surface of water.

What will be the apparent approximate weight of the steel?

In other words, how much approximate force would you have to exert to lift the steel under waater?

62.4 lb

480 lb

418 lb

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Explanation

Calculate how much of a wood volume will remain under water when it floats

1 pts

A cubic foot of pine wood weighs about 30 pounds. If it were pushed underwater, the byoyant force on it would also be 62.4 lb. But since the byoyant force is greater than its weight, pine will not stay underwater unless held there.

Calculate how much of its volume will remain under water when it floats.

To do this, we reason that it will sink in the water until it is buoyed up by a force that is equal to its weight.

What weight of water will the 30-lb piece of wood have to displace in order to float? (1) lb
What is the volume of this weight of water? (2) ft³
How much of the wood will be below water level as the block of wood floats? (3) ft³

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Calculate the following

1 pts

A cubic foot of pine wood weighs about 30 pounds. If it were pushed underwater, the byoyant force on it would also be 62.4 lb. But since the byoyant force is greater than its weight, pine will not stay underwater unless held there.

One can determine what fraction of a floating object will be under a liquid by dividing the density of the object by the density of the liquid.
Given 0.48 ft³ of wood is under water.

What is the density of the wood? (1) lb/ft³
What is the density divided by the density of water? (2)
Suppose a piece of oak wood flats with 62 percent of its volume underwater. What is the density of the wood? (3) lb/ft³

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Determine the apparent weight in water

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As in calculating pressure, we must use the weight density rather than the mass density in calculations involving buoyancy. Let us determine the apparent weight in water of a 5-cm³ piece of aluminum-about pencil size. (The specific gravity of aluminum is 2.7)

what is the weight density of aluminum in N/m³? (1) N/m³
what is the weight density in N/cm³? (2) N/cm³
how much does the piece of aluminum weigh? (3) N
what is the weight density of water in SI units? (4) N/m³
cover this to N/cm³ (5) N/cm³
what is the buouant force of 5 cm³ aluminum? (6) N
what is the apparent weight of the aluminum in water? (7) N

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The Origin of Buoyant Force

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volume_mute

What is the primary physical cause of the upward buoyant force experienced by an object when it is submerged in a fluid?

The difference in fluid pressure between the bottom and the top of the object.

The molecular repulsion between fluid molecules and the solid surface.

Atmospheric pressure pressing down harder on the surrounding fluid surface.

The horizontal pressure vectors squeezing the sides of the object inward.

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Submerged Volume Displacement

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volume_mute

A completely submerged solid block has a total physical volume of \(1.5\text{ ft}^3\). What volume of water does it displace?

1.5 ft³

93.6 ft³

0.75 ft³

It depends on the mass density of the block material.

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Explanation

Archimedes' Principle Core Definition

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volume_mute

According to Archimedes' principle, the magnitude of the upward buoyant force acting on a submerged object is directly equal to which of the following properties?

The weight of the fluid that the object displaces.

The true weight of the object measured in a vacuum.

The total volume of the fluid remaining in the container.

The mass of the object multiplied by its surface area.

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Explanation

Calculating Buoyant Force

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Water has a weight density of approximately \(62.4\text{ lb/ft}^3\). If a solid cube with a volume of \(2\text{ ft}^3\) is held completely underwater, calculate the upward buoyant force acting on it.

Answer = (1)

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Apparent Weight Underwater

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A heavy stone block weighs \(150\text{ lb}\) in the air. When it is completely submerged underwater, it displaces a volume of water that weighs \(50\text{ lb}\). What is the apparent weight of the stone block while it is underwater?

Answer = (1)

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Explanation

Sinking vs. Floating Mechanics

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Match the net force conditions below to the resulting mechanical behavior of an object placed in a fluid.

To complete the line match

Click on an item in the first group
Click on the match in the second group

To delete a match, double click on a line

Conditions

Buoyant force is less than the object's total weight

Buoyant force is equal to the object's total weight when fully submerged

Buoyant force is greater than the object's weight when fully submerged

Behaviors

The object sinks down to the bottom

The object hovers in baseline equilibrium at any depth

The object rises up to the surface and floats

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Explanation

Floating Equilibrium Force

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volume_mute

A block of wood weighing \(35\text{ lb}\) is dropped into a lake. It breaks the surface and then comes to rest, floating stably. What is the exact value of the upward buoyant force acting on the wood while it floats?

35 lb

62.4 lb

0 lb

It cannot be determined without knowing the total volume of the block.

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Explanation

Predicting Behavior via Density

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An unknown solid material has a mass density that is strictly less than the mass density of the liquid it is dropped into. Fill in the placeholder to complete the statement detailing the behavior of the solid:

Because its density is lower than the fluid, the object will (1) to the surface.

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True or False: Buoyant Force vs Depth

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volume_mute

Determine if the following scientific statement is true or false:

"As a fully submerged solid iron ball sinks deeper and deeper into a deep body of water, the upward buoyant force acting on it increases drastically due to the rising water pressure."

true

false

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Explanation

The Influence of Geometric Shape

1 pts

volume_mute

A solid block of steel sinks straight to the bottom of a pool. However, if the same amount of steel is rolled thin and shaped into a hollow boat hull, it floats easily. Why does altering the geometric shape allow the steel to float?

The hollow shape encloses air, significantly increasing the overall volume of displaced water and maximizing the potential buoyant force.

Shaping steel into thin sheets alters the fundamental atomic mass density of the element.

The flat, curved surfaces of a hull eliminate the downward force of atmospheric pressure entirely.

Water pressure is incapable of applying upward vertical vectors to solid block shapes.

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An object in a fluid is buoyed up by a force ______ the weight of the fluid displaced

Correct Answer

Explanation

What is the buoyant force exerted on a cubic foot of steel by the water?

Correct Answer

Explanation

how much force would you have to exert to lift the steel under water?

Correct Answer

Explanation

Calculate how much of a wood volume will remain under water when it floats

Correct Answer

Explanation

Calculate the following

Correct Answer

Explanation

Determine the apparent weight in water

Correct Answer

Explanation

The Origin of Buoyant Force

Correct Answer

Explanation

Submerged Volume Displacement

Correct Answer

Explanation

Archimedes' Principle Core Definition

Correct Answer

Explanation

Calculating Buoyant Force

Correct Answer

Explanation

Apparent Weight Underwater

Correct Answer

Explanation

Sinking vs. Floating Mechanics

Conditions

Behaviors

Correct Answer

Explanation

Floating Equilibrium Force

Correct Answer

Explanation

Predicting Behavior via Density

Correct Answer

Explanation

True or False: Buoyant Force vs Depth

Correct Answer

Explanation

The Influence of Geometric Shape

Correct Answer

Explanation

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