Mass: Mass is a measure of amount of matter an object has got. It is measured in terms of kilograms or Kg in SI units. It is denoted by the letter ‘m’. Mass of a body is constant. Its value remains same even if its position is changed. In other terms it is a scalar quantity. If the mass of an object is 100 kg its mass remains same even if you take it to moon.
Mass of an unknown body is measured using a balance. A mass of known weight such as 1 kg or 2 kg is kept at one side of the balance and the unknown body is kept at the other side of the balance. Now we add/remove the numbers on the known side of the mass and calculate the mass of the unknown object.
Density is a physical quantity of an object. It is the amount of matter present in unit volume of that object. It varies from one object to other. It is denoted by the symbol ‘ρ’ (rho).
ρ =Density in Kg/m^3 in SI units
M=mass in kilograms
V=Volume in Cubic meters
It is a very important concept while calculating the buoyancy of an object. To find out the density of an object knowing its volume is a must. The volume of a regular object is calculated by measuring the length, width and height of that object. And for an irregular object the volume has to be found out by the ‘displacement of fluid’ method. Density also depends on pressure and temperature of that object. Density is directly proportional to pressure and inversely to temperature.
Mathematically V=length X width X Height
Length, width and height are in meters and volume in Cubic meters
The following list shows the density of different materials in kg/m^3
Question: Find the mass an Iron block having dimensions length="500cm," width="350cm" and height="850cm.
Given: L="500cm" or 0.5m
W="350cm" or 0.35m
H="850cm" or 0.85m
From the above table Density of Iron="7874" Kg/m^3
Mass =Density X volume
=Density X (L X W X H)
=7874 X (0.5X0.35X0.85) ( Kg/ m^3) (mXmXm)
Mass =1171.25 Kilograms
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