Answer:
Density of the fuel is 727.3 kilograms per cubic meter.
Specific weight of the fuel is 7127.3 Newtons per cubic meter.
Specific gravity of the fuel is 0,727.
Explanation:
In order to use SI units, we have to convert liters to cubic meters. Knowing that a liter is a cubic decimeter and a cubic decimeter is [tex]1*10^{-3}[/tex] cubic meters, we know that the tank has 0,055 cubic meters of fuel (because it is full).
Now that we have things in SI units, we calculate density:
[tex]p_{fuel}= \frac{mass}{volume} = \frac{40 kg}{0.055 m^{3} } =727.3 \frac{kg }{m^{3} }[/tex]
Knowing the mass per unit of volume, we can calculate weight per unit of volume thanks to Newton's second law (mass times acceleration, g in this case, equals force (weight)), i.e. specific weight:
[tex]y=p*g=727,3 \frac{kg}{m^{3}}*9.8\frac{m }{s^{2}}=7127,3 \frac{N}{m^{3}}[/tex]
With density we can also calculate how dense the fuel is related to a reference (water), i.e. specific gravity. SG is a dimensionless number that tell us how much denser (SG>1) or lighter per unit of volume (SG<1) a substance is than water. We use water as a reference because it is one of the most used substances in our life, and it is a standard density (1000 kg per cubic meter at 4°C and 1 atm).
[tex]SG=\frac{p_{fuel} }{p_{water} } =\frac{727.3 \frac{kg }{m^{3} }}{1000 \frac{kg }{m^{3} }} =0,727[/tex]
