What is the correct density of the cork based on its buoyancy and weight?

In summary, the conversation involves finding the density of a large piece of cork using a spring scale and the concept of buoyancy. The attempt at a solution involved finding the mass and buoyant force, calculating the volume of the object, and using the density formula. However, there was confusion about the direction of forces and the meaning of "Fb." The correct answer was not obtained due to errors in calculation of the buoyant force.
  • #1
awertag
64
0

Homework Statement



A large piece of cork weighs 0.224 N in air. When held submerged underwater by a spring scale as shown in Figure 13-27, the spring scale reads 0.672 N. Find the density of the cork.

Homework Equations



Fb=buoyant force

The Attempt at a Solution


i found mass by doing .224/9.8 so mass=2.286e-2 kg
then i got Fb by doing weight in air minus weight in water so Fb=-.448 N
then i did Fb=(densitywater)(volumeobject)(g) and got the volume of object so volume=4.571e-5 cubic m
last i did density=mass/volume and got the incorrect answer of 5000 kg/cubic meter

If anyone can help me, I don't know where I went wrong. Thanks very much, awe.g
 
Last edited:
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  • #2
What's an Fb when it's at home? There's no attached figure.
 
  • #3
what do you mean at home? sorry I am confused
 
  • #4
idk if that's what you want...justr a picture, doesn't show much though
 

Attachments

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  • #5
awertag said:
what do you mean at home? sorry I am confused

Sorry, it's just an expression. Take a look at the directions that the forces act, and re-evaluate your value for Fb.
 
  • #6
oh ok lol. what does the expression mean exactly? Like originally?

and would Fb be equal to mg?
 
  • #7
The expression is an inquiry as to what something (or someone) really is.

Fb is the force of buoyancy. It's opposing the weight of the object. Check your calculation for Fb.
 

1. What is buoyancy?

Buoyancy is the upward force exerted by a fluid on an object immersed in it. It is a result of the difference in pressure between the bottom and top of the object, and the greater pressure at the bottom pushes the object up.

2. How is density related to buoyancy?

Density is a measure of how tightly packed the particles in a substance are. Objects with a higher density than the surrounding fluid will sink, while objects with a lower density will float. This is because the fluid exerts more pressure on the object with higher density, causing it to sink.

3. How does the shape of an object affect its buoyancy?

The shape of an object does not affect its buoyancy, as long as the object's volume and density remain the same. However, the shape may affect how the object displaces the fluid, which can impact the amount of buoyant force acting on it.

4. How do you calculate the buoyant force on an object?

The buoyant force on an object can be calculated using Archimedes' principle, which states that the buoyant force is equal to the weight of the fluid displaced by the object. This can be calculated by multiplying the density of the fluid by the volume of the displaced fluid and the acceleration due to gravity.

5. Can an object have negative buoyancy?

Yes, an object can have negative buoyancy if its density is greater than the density of the surrounding fluid. In this case, the object will sink instead of floating. This can be seen in objects such as rocks, which have a higher density than water.

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