Buyoancy Question the day before the final

  • Thread starter addnecro
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In summary, the density of the glass making up the beaker is 2786 kg/m^3. To calculate this, you can use the formula Fb= density*g* Volume displaced, where Fb is the buoyancy force, g is the acceleration due to gravity, and Volume displaced is the volume of water displaced by the beaker. The maximum water volume the beaker can displace is 5*10^-4 m^3. When the beaker starts to sink, its mass (including water inside) is 0.25 kg. The mass of water displaced is 0.5*density of water*volume of beaker. The mass of the water inside the beaker is making it sink to the
  • #1
addnecro
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You place a beaker partly filled with water, into a sink. The beaker itself has a mass of 390grams and an interior volume of 500 cm^2. You now start to fill the sink with water and you f ind that if the beaker is less than half full, it floats but it is more than half full it sinks to the bottom.

What is the density of the glass making up the beaker?

The answer is 2786 kg/m^3

How do you do this? argh i got my final tomorrow =S

Homework Statement



mass of beaker=0.39 kg
density of water is 1000 kg/m^3
interior volume of beaker is 500 cm^2

Homework Equations



Fb= density*g* Volume displaced

The Attempt at a Solution


i don't know how to do this AT ALL!
 
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  • #2
What is the maximum water volume the beaker can displace?

What is its mass (including water inside) if it starts to sink?
 
  • #3
max water the beaker can displace is
mg= density*gravity*volume
0.390 = 1000 x volume
volume=3.9*10^-4

Mass (including water) when it starts to sink...
0.5*density*volume
0.5*1000*5*10^-4=0.25 kg
 
  • #4
addnecro said:
max water the beaker can displace is
mg= density*gravity*volume

No. Think - if you put 500 mL beaker in water up to the rim, how much water was displaced?
 
  • #5
ummm 5x10^-4 m^3
 
  • #6
Yes. m3 is not the easiest unit to work with in this case, but it is correct (just inconvenient).

What mass of water was displaced?

If beaker starts to sink, what does it tell about its mass?
 
  • #7
is the mass of water displaced 0.5*density of water*volume of beacker..
as the beaker starts to sink, it tells me that the mass will is increasing?
 
  • #8
addnecro said:
is the mass of water displaced 0.5*density of water*volume of beacker..

Why 0.5?

as the beaker starts to sink, it tells me that the mass will is increasing?

:bugeye:
 
  • #9
haha i meant as the beaker starts to sink, we know that the mass of the water inside the beaker is making it sink to the bottom.
It is 0.5 because it's half the volume of the beaker =)
 
  • #10
V(outer voume of beaker)*g*1000 = v/2(v=inner volume)*g*1000 + m(m=mass of beaker)*g


v=500cm^3 = 500*10^-6 m^3
g=10m/s^2
m=390gm=.39kg

then density = mass of beaker / volume of beaker


volume of beaker = V-v
 
  • #11
Thanks
 
  • #12
did u get it?
 
  • #13
ok ur welcome
 

Related to Buyoancy Question the day before the final

1. What is buoyancy and how does it relate to the final exam?

Buoyancy is the upward force that a fluid exerts on an object placed in it. This force is equal to the weight of the fluid that the object displaces. In the context of a final exam, buoyancy may be used as an analogy to explain how studying and preparation can help to lift a student's grades and confidence.

2. How can understanding buoyancy help me with my final exam?

Understanding the concept of buoyancy can help with time management and prioritization of topics to study. Just as a heavy object will sink in water unless it displaces enough water, focusing on the important topics and studying them thoroughly can help you stay afloat during the final exam.

3. Can buoyancy be applied to other subjects besides physics?

Yes, the concept of buoyancy can be applied to other subjects such as chemistry, biology, and even math. In chemistry, buoyancy is used to explain the behavior of fluids and gases. In biology, it can be used to understand the adaptations of aquatic animals. In math, buoyancy can be used to solve problems involving volume and density.

4. Is there a formula for calculating buoyancy?

Yes, the formula for calculating buoyancy is Fb = ρVg, where Fb is the buoyant force, ρ is the density of the fluid, V is the volume of the displaced fluid, and g is the acceleration due to gravity. This formula is commonly used in physics and can be applied to various scenarios involving buoyancy.

5. How can I improve my understanding of buoyancy before the final exam?

One of the best ways to improve your understanding of buoyancy is to practice problems and examples. You can also read up on the concept and its applications in various subjects. Additionally, seeking help from a teacher or tutor can also aid in your understanding and preparation for the final exam.

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