Calculate mass of tank floating in freshwater

[Parsifal1]

Homework Statement

A rectangular tank contains 6L of freshwater, has a floor area of 0.3m^2 and floats upright in freshwater. If the bottom of the tank is 150mm below the surface of the water, calculate the mass of the tank.

Homework Equations

F=P*A=pgAh

The Attempt at a Solution

1000*9.81*0.3*0.15=441.54N 441.45/9.81=45kg

 

[billy_joule]

A rectangular tank contains 6L of freshwater... calculate the mass of the tank.

I think you're expected to find the mass of just the tank( excluding the water).

 

[Parsifal1]

I think you're expected to find the mass of just the tank( excluding the water).

That's what I don't understand, 6L=6Kg, should it be mass=0.03*1000=mass*density?

 

[billy_joule]

You've found the mass of the tank and water in post #1; 45kg.
If there's 6kg of water in the tank, how much does just the tank weigh?

 

[Parsifal1]

You've found the mass of the tank and water in post #1; 45kg.
If there's 6kg of water in the tank, how much does just the tank weigh?

-15Kg? How can the mass of the tank and the water weigh less than the water? Am I using the right formula for the mass of the tank+water?

 

[Parsifal1]

Should I do 0.3*0.15*1000=P=pyh=45 Then take 45 from 60? I get the wrong answer by doing that? :/

 

[Parsifal1]

If the weight of the water displace=buoyant force, then is the mass of the tank the buoyant force over 9.81? As the mass of the object is equal to the mass of water displaced.

 

[Parsifal1]

I found the answer:

density=mass/volume
mass=density*volume
1000*(0.3*0.15)=45
45-6=39Kg

Thanks for the help.