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### Re: Density Lab B

Posted: February 28th, 2020, 6:00 am
A second question: How would you find the mass of an object with unknown density using Archimedes' principle? Why would this work?

### Re: Density Lab B

Posted: February 28th, 2020, 12:56 pm
I don't think you can find the Mass without both volume and density. SInce the equation is p = m/v, it would be the equivalent of saying 23 * 5y = 2x. I don't think you'll be able to find the mass without the other two.

### Re: Density Lab B

Posted: March 1st, 2020, 7:21 pm
NSCDS3RdCaptain wrote:
February 28th, 2020, 6:00 am
A second question: How would you find the mass of an object with unknown density using Archimedes' principle? Why would this work?
Float it in some kind of boat?

Try this: place a suitably-sized boat in a graduated measuring vessel filled with water, and record the water level. Add your unknown object, record the change in water level. The difference between the two is the mass of the object.

### Re: Density Lab B

Posted: March 2nd, 2020, 3:39 pm
Thank you so much. But I still have some questions:
What units of volume to what units of mass?
Why does this work?

### Re: Density Lab B

Posted: March 3rd, 2020, 8:33 am
NSCDS3RdCaptain wrote:
March 2nd, 2020, 3:39 pm
Thank you so much. But I still have some questions:
What units of volume to what units of mass?
Why does this work?
OK.

For something to float, the buoyant force must equal the weight of the object.
Archimedes' principle tells you that the buoyant force on an object is equal to the weight of the fluid that is displaced.
So if you have a floating boat, and you add your mystery object to it, the boat's weight increases by the weight of the object, so the boat will sink a bit, and displace an additional volume of water with the weight of your mystery object in order to reach equilibrium.
You measure the displaced water volume as an increase in the water level.

You know that the density of water is approx. 1g cm^-3, so you know the mass of the extra displaced water, which is equal to the mass of the object.

(If you want to find the density of the mystery object as well, you could submerge it in water to find its volume. You might have to add weight to sink it if it's less dense than water.)