# Homework Help: Relating density and volume

1. Aug 12, 2009

### DSG3002

1. The problem statement, all variables and given/known data

How big is a ton? That is, what is the volume of something that weighs a ton? To be specific, estimate the diameter of a 1-ton rock, but first make a wild guess: will it be 1ft across, 3ft, or the size of a car? [Hint: Rock has mass per volume about 3 times that of water, which is 1kg per Liter (1000cm) or 62lbs per cubic foot.]

2. Relevant equations

3. The attempt at a solution

Well finding the volume of the ton is easy:

3 kg/L = density of rock, so volume would be 333.3 repeating Liters.

However, I'm not sure how to answer the original question "how big is a ton?" Anybody have a clear idea what's being asked? This is off a worksheet.

2. Aug 12, 2009

### Dick

A liter is 1/1000 of a cubic meter, isn't it? So 333 liters is 1/3 of cubic meter. The question, I think, is asking for the edge size of a cube that has that volume.

3. Aug 12, 2009

### DSG3002

I'm unfamiliar with what edge size is and how to find it; I'm just beginning taking Physics this semester. It talks about estimating the diameter of a 1-ton rock, but is doing so no longer necessary due to already having the volume, or am I overlooking something?

You don't think answering with the volume alone is answering the question?

4. Aug 12, 2009

### Dick

No, I don't think it's quite enough. They are asking whether it is '1 ft across'. Sounds like they are actually talking about a sphere. The volume of a sphere is (4/3)*pi*r^3 where r is the radius. Set that equal to 1/3 m^3 and solve for r.