Question

section 2.2 review

1. define density, write the formula (from memory!), and give two different units used to measure density.
2. one cubic centimeter (cm³) is the same volume as one
3. a materials density is the same, no matter how large or small the sample is, or what its shape is, as long as it is a solid, uniform piece of the material. explain how this is possible and give an example.
4. the density of balsa wood is about 170 kg/m³. convert to g/cm³. why do you think balsa wood, rather than oak or ash, is commonly used for building models? (use evidence from figure 2.9 on page 37.)
5. a certain material has a density of 0.2 g/cm³. is this material better for building a bridge or for making sofa cushions? explain, using evidence from figure 2.9 on page 37.
6. the piece of wood shown above has a mass of 20 grams. calculate its volume and density. then, use figure 2.9 on page 37 to determine which type of wood it is. what are the two factors that determine a materials density?
7. the density of maple wood is about 755. kg/m³. what is the mass of a solid piece of maple that has a volume 640. cm³?

two toy - blocks are made of the same type of material. one has a mass of 20 grams and its dimensions are 2 cm×4 cm×1 cm. the second block measures 4 cm×3 cm×2 cm. calculate the mass of the second block.

Explanation:

Step1: Calculate the density of the first block

The volume of the first block $V_1 = 2\times4\times1=8$ $cm^3$. The mass $m_1 = 20$ g. The density $
ho=\frac{m}{V}$, so $
ho=\frac{20}{8}=2.5$ g/cm³.

Step2: Calculate the volume of the second block

The volume of the second block $V_2=4\times3\times2 = 24$ $cm^3$.

Step3: Calculate the mass of the second block

Since the two blocks are of the same material, they have the same density. Using the formula $m=
ho V$, with $
ho = 2.5$ g/cm³ and $V = V_2=24$ $cm^3$, we get $m = 2.5\times24=60$ g.

Answer:

60 g