The Math Forum

Ask Dr. Math - Questions and Answers from our Archives
Associated Topics || Dr. Math Home || Search Dr. Math

Relative Density

Date: 05/18/2000 at 02:01:08
From: Chris Guerra
Subject: density

Is this physics problem possible?

A solid object floats in water with three-fourths of its volume 
beneath the surface. What is the object's density?

Date: 05/18/2000 at 08:55:14
From: Doctor Rick
Subject: Re: density

Hi, Chris.

Yes, the problem can be solved.

The floating object displaces a volume of water equal to 3/4 of its 
own volume. Let's say the volume of the object is V. The volume of 
displaced water is then (3/4)V. 

The density of water is 1 gram/cm^3 (a gram was defined so that this 
would be true). Mass equals density times volume, so you can write an 
expression for the mass M of the displaced water.

The volume of water displaced by a floating object is equal to the 
mass of the object. Therefore the object also has mass M. The density 
of the object is defined as M/V. You can do the rest.

- Doctor Rick, The Math Forum   
Associated Topics:
High School Basic Algebra
High School Physics/Chemistry

Search the Dr. Math Library:

Find items containing (put spaces between keywords):
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

Submit your own question to Dr. Math

[Privacy Policy] [Terms of Use]

Math Forum Home || Math Library || Quick Reference || Math Forum Search

Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.