Buoyancy

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

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QUESTION OF
Views #: 101
Questions #: 6
Time: 10 minutes
Pass Score: 80.0%
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An object in a fluid is buoyed up by a force ______ the weight of the fluid displaced

1 pts
volume_mute
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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?

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Explanation

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

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.
  1. What is the density of the wood? (1) lb/ft3 
  2. What is the density divided by the density of water? (2)
  3. 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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Explanation

Determine the apparent weight in water

1 pts

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) 

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

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0 . EXP ÷ MR
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