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Pressure, Buoyant Force problem

  • #1

Homework Statement


A solid cube of unkown material is floating upright in water so that 1/4 of the cube is above the surface of the water. What is the density of the material?


Homework Equations


Density=m/v
F=mg
Fb=density of fluid times volume of the fluid times g
P=density times height times g

The Attempt at a Solution


Since the cube is floating upright in the water I think that means that the force of weight is equal to the buoyant force.
P=density times h times g
P=1000 kg/m^3 times 1/4 times 9.80 which equals 2450 Pa
Then I used F=PA
F=2450 Pa times 1/4 which equals 612.5 N
Then I used F=mg
m=F/g
m=612.5 N/9.80 m/s^2
m=62.5 kg
I dont know what 2 do from there and I think one of my step is wrong because I multiplied the area by 1/4 but I dont think that's right can someone please help me and explain 2 me how to solve this problem
 

Answers and Replies

  • #2
5
0
(Density of the object / density of the fluid) x 100 = Prencentage of object's volume in the fluid
 
  • #3
But when I do that I get the following:
b/1000 kg/m^3 times 100=3/4
100b/1000=3/4
1b/10=3/4
b=7.5 and b is the density of the object but on my sheet it says the answer is 750 kg/m^3 and its almost like my answer but the decimal is moved over and idk y. Maybe my work was wrong or something can u explain ?
 
  • #4
(Density of the object / density of the fluid) x 100 = Prencentage of object's volume in the fluid
But when I do that I get the following:
b/1000 kg/m^3 times 100=3/4
100b/1000=3/4
1b/10=3/4
b=7.5 and b is the density of the object but on my sheet it says the answer is 750 kg/m^3 and its almost like my answer but the decimal is moved over and idk y. Maybe my work was wrong or something can u explain ?
 
  • #5
5
0
3/4=0.75 is not the Precentage dude, it's 75%
 

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