Density and Specific Gravity in Physics Problems

By Consumer Dummies

Using physics, you can show how mass and volume are related to density. You can also calculate the specific gravity of a material, such as gasoline, if you know its density.

Here are some practice questions that you can try.

Practice questions

  1. You make a cake that has a mass of 300 grams and fits in a cake pan that is 30 by 10 by 6.0 centimeters cubed. What is the density of the cake?

  2. A box of cough drops has a mass of 1.0 gram, and its dimensions are 1.0 by 5.0 by 8.5 centimeters cubed. It contains 30 cough drops, each of which has a mass of 2.2 grams. What is the density of the box when it is full of cough drops?

  3. The density of gasoline is 721 kilograms per cubic meter. What is its specific gravity?

Answers

The following are the answers to the practice questions:

  1. image0.png

    Density is mass per unit volume, or

    image1.png

    In this case, the mass is

    image2.png

    The volume is

    image3.png

    Insert these values into the equation for density to find the density of the cake:

    image4.png

  2. image5.png

    Density is mass per unit volume, or

    image6.png

    The total mass of the box plus cough drops is

    image7.png

    The volume of the box is

    image8.png

    Insert these values into the equation for density to find the density of the box:

    image9.png

  3. 0.721

    Specific gravity is the density of a material divided by the density of water at

    image10.png

    which is 1,000 kilograms per cubic meter. The equation for specific gravity is

    image11.png

    The subscript x refers to the material in question. You know that

    image12.png

    Insert this value into the equation for specific gravity to find

    image13.png