Question

The average particle density in the Milky Way galaxy is about one particle per cubic centimeter. Express this number in SI units $\left(\mathrm{kg} / \mathrm{m}^{3}\right)$ . Indicate any assumptions you made.

Name: Problem 4, Chapter 9: College Physics
Uploaded: 2020-04-09T01:20:02-08:00
Duration: 2 min 35 s
Channel: Farhanul Hasan
Description: The average particle density in the Milky Way galaxy is about one particle per cubic centimeter. Express this number in SI units (kg / m^3) . Indicate any assumptions you made.

   The average particle density in the Milky Way galaxy is about one particle per cubic centimeter. Express this number in SI units $\left(\mathrm{kg} / \mathrm{m}^{3}\right)$ . Indicate any assumptions you made.

College Physics

Eugenia Etkina,… 1st Edition

Chapter 9, Problem 4

Instant Answer

Solved by Expert Farhanul Hasan

04/09/2020

Step 1

We need to convert this to SI units, which are kilograms per cubic meter. Show more…

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The average particle density in the Milky Way galaxy is about one particle per cubic centimeter. Express this number in SI units $\left(\mathrm{kg} / \mathrm{m}^{3}\right)$ . Indicate any assumptions you made.

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Key Concepts

Unit Conversion

Converting units from one system to another is crucial. In this context, the conversion involves turning a volume unit of cubic centimeters (cm³) into cubic meters (m³). Since 1 m = 100 cm, it follows that 1 m³ = (100 cm)³ = 1×10^6 cm³, meaning that 1 cm³ is 1×10^(-6) m³.

Assumption on Particle Mass

In converting a number density (particles per volume) into a mass density (kg/m³), one must assume a mass for each particle. A typical assumption in astrophysics is that the particles are hydrogen atoms, each having a mass of approximately 1.67×10^(-27) kg.

Density Calculation

The density in SI units is calculated by multiplying the number density (converted into particles per m³) by the mass per particle. With one particle per cm³, which is equivalent to 1×10^6 particles per m³, and assuming a mass of 1.67×10^(-27) kg per particle, the resulting mass density is about 1.67×10^(-21) kg/m³.

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