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Buoancy force question

  • Thread starter lbella026
  • Start date
  • #1
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Homework Statement


A cube made from iron has sides equal to 20cm/side. The density of iron is 7860kg/m^3. The cube is completely submerged in water; the density of water is 1000kg/m^3. What is the buoancy force acting on the cube.


Homework Equations


W(DL)= (D(L))(V)(g)


The Attempt at a Solution


W(DL)=(1000kg/m^3)(8000cm^3)(10m/s^2) =8x10^7 Neutons
Im not sure if this answer is correct ????
 

Answers and Replies

  • #2
Galileo
Science Advisor
Homework Helper
1,989
6
Take care of your dimensions. You're using the density in kg per meter^3, but volume in cm^3.
1 Newton is 1 [itex]kg m s^{-2}[/itex] You can get the right units from there.
When in doubt, always use SI-units.
 
  • #3
ehild
Homework Helper
15,409
1,813
Force of buoyancy = weight of the water displaced by the cube. How can that small cube of water weight 8x10^7 newtons?

Think, what is your weight? less or more than 8x10^7 N? Your average density is also very close to 1000 kg/m^3. Are you bigger or smaller than that 20x20x20 cm^3 cube?


ehild
 

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