Problem Statement
One litre of crude oil weighs 9.6 N. Calculate its specific weight, density, and specific gravity.
Given Data
- Volume, \(V = 1.0 \, \text{litre}\)
- Weight, \(W = 9.6 \, \text{N}\)
Solution
1. Convert Volume to SI Units (m³)
The standard unit for volume in these calculations is cubic metres (m³).
2. Calculate Specific Weight (\(\gamma\))
Specific weight is defined as weight per unit volume.
3. Calculate Density (\(\rho\))
Density is related to specific weight by the acceleration due to gravity, \(g \approx 9.81 \, \text{m/s}^2\).
4. Calculate Specific Gravity (\(S.G.\))
Specific gravity is the ratio of the density of the substance to the density of a reference substance, usually water (\(\rho_{\text{water}} \approx 1000 \, \text{kg/m}^3\)).
Specific Weight: \( \gamma = 9600 \, \text{N/m}^3 \)
Density: \( \rho \approx 978.6 \, \text{kg/m}^3 \)
Specific Gravity: \( S.G. \approx 0.979 \)
Explanation of Terms
Specific Weight (\(\gamma\)): This measures how much a certain volume of a substance weighs. It depends on both the substance’s mass and the force of gravity. It’s useful in civil and mechanical engineering for calculating forces exerted by fluids.
Density (\(\rho\)): This is an intrinsic property of a substance, measuring its mass per unit volume. Unlike weight, density does not change with location (i.e., it’s independent of gravity).
Specific Gravity (\(S.G.\)): This is a dimensionless ratio that compares the density of a substance to the density of water. If \(S.G. > 1\), the substance is denser than water and will sink. If \(S.G. < 1\), it is less dense and will float.
Physical Meaning
The results tell us several things about this crude oil. Its specific gravity of approximately 0.979 is less than 1, which confirms that this crude oil will float on water, as expected.
The density of 978.6 kg/m³ shows that a cubic metre of this oil has a mass of about 978.6 kilograms. This is slightly less than the 1000 kg mass of a cubic metre of water. These properties are fundamental in the oil and gas industry for transportation, storage, and processing calculations.
