Chapter 1: Problem 40
A \(5-\mathrm{m}^{3}\) container is filled with \(900 \mathrm{~kg}\) of granite (density of \(2400 \mathrm{~kg} / \mathrm{m}^{3}\) ). The rest of the volume is air, with density equal to \(1.15 \mathrm{~kg} / \mathrm{m}^{3}\). Find the mass of air and the overall (average) specific volume.
Short Answer
Expert verified
Mass of air is approximately 5.32 kg. The overall specific volume is about 0.00552 m³/kg.
Step by step solution
01
Calculate the Volume Occupied by Granite
The density of granite is given as \(2400 \, \text{kg/m}^3\). By using the formula for density, \( \text{Density} = \frac{\text{Mass}}{\text{Volume}} \), we can find the volume of the granite. Rearrange the formula to solve for volume: \( \text{Volume} = \frac{\text{Mass}}{\text{Density}} \). Substitute the given values: \( \text{Volume of Granite} = \frac{900 \, \text{kg}}{2400 \, \text{kg/m}^3} = 0.375 \, \text{m}^3 \).
02
Calculate the Volume Occupied by Air
The total volume of the container is \(5 \, \text{m}^3\). Since part of this is occupied by granite, subtract the volume of granite (calculated in Step 1) from the total volume to find the volume occupied by air: \( \text{Volume of Air} = 5 \, \text{m}^3 - 0.375 \, \text{m}^3 = 4.625 \, \text{m}^3 \).
03
Calculate the Mass of Air
Using the density of air given as \(1.15 \, \text{kg/m}^3\), calculate the mass of the air using the formula \( \text{Mass} = \text{Density} \times \text{Volume} \). Substitute the values we found: \( \text{Mass of Air} = 1.15 \, \text{kg/m}^3 \times 4.625 \, \text{m}^3 = 5.31875 \, \text{kg} \).
04
Calculate the Overall Specific Volume
The total mass in the container is the sum of the mass of granite and the mass of air, which is \(900 \, \text{kg} + 5.31875 \, \text{kg} = 905.31875 \, \text{kg} \). The specific volume \(u\) is given by \(u = \frac{\text{Total Volume}}{\text{Total Mass}}\). Substitute the values to get \(u = \frac{5 \, \text{m}^3}{905.31875 \, \text{kg}} \approx 0.00552 \, \text{m}^3/\text{kg}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Density Calculation
Density is a fundamental property of matter that describes the mass per unit volume of a substance. It offers a way to determine how compact a material is within a defined space.
To calculate density, we use the formula:
To calculate density, we use the formula:
- Density, \( \rho = \frac{\text{Mass}}{\text{Volume}} \)
- \( \text{Volume} = \frac{\text{Mass}}{\text{Density}} \)
- \( \text{Volume of Granite} = \frac{900 \text{ kg}}{2400 \text{ kg/m}^3} = 0.375 \text{ m}^3 \)
Specific Volume
Specific volume is a useful concept in thermodynamics, representing the volume occupied per unit mass of a substance. It is essentially the inverse of density and is often denoted by the letter \( v \).
The formula to calculate specific volume is:
The formula to calculate specific volume is:
- \( v = \frac{\text{Volume}}{\text{Mass}} \)
- Total Mass = 900 kg (granite) + 5.31875 kg (air) = 905.31875 kg
- \( v = \frac{5 \text{ m}^3}{905.31875 \text{ kg}} \approx 0.00552 \text{ m}^3/\text{kg} \)
Mass Calculation
To determine the mass of a substance when its density and volume are known, we use the following relationship:
- Mass = Density \( \times \) Volume
- Volume of Air = Total Volume - Volume of Granite = 5 m³ - 0.375 m³ = 4.625 m³
- Density of Air = 1.15 kg/m³
- Mass of Air = 1.15 kg/m³ \( \times \) 4.625 m³ = 5.31875 kg
Volume Calculation
Calculating volume involves understanding how much space an object or substance occupies, typically described in cubic meters (m³) or liters. The relationship between mass, density, and volume is given by the equation:
- Volume = \( \frac{\text{Mass}}{\text{Density}} \)
- Using the formula, we find the Volume of Granite = \( \frac{900 \text{ kg}}{2400 \text{ kg/m}^3} = 0.375 \text{ m}^3 \)
- Once we know how much space granite occupies, the remaining volume of the container is the space taken up by air: Volume of Air = 5 m³ - 0.375 m³ = 4.625 m³