5what is the mass of a single fin made with card stock #1 (see the table above) and with these dimensions: 0.1865 cm x 5.75 cm x 8.8 cm? 9.44 cm3

Notice that this problem involves three variables: mass, density and volume. These three are related through this formula:

Density = Mass/Volume
So, to find for mass,
Mass = Density*Volume

The volume can be calculated using the dimensions.
V = 0.1865 cm x 5.75 cm x 8.8 cm = 9.44 cm³

Now, the density is a constant value for solids. Since card stock is made of paper, we can use the density of paper: 0.25 g/cm³. Thus,
Mass = 0.25 g/cm³ * 9.44 cm³
Mass = 2.36 g

The rocks expand when there hot/warm  and contract when they are cold.

490 n  f=125n a=2.5m/s2