Let's start the journey and learn all the concepts involved in the process of calculating Object Density:
Today we will learn and understand concepts of density of an object.
Density of an object is defined as
“ mass per unit volume “ OR
“ total number of particles per unit volume “ OR
“ the number of atoms , molecules or ions per unit volume is also called density . OR
“ Mass of particles per unit volume “ . OR
“ Quantity of matter per unit volume “ .
Quantity: It is a derived scalar physical quantity no need for direction.
Symbol: It is represented by “ D “ or “ d” or “ ρ “
Mathematical formula: It can be expressed as D = mass/volume Or D = m/v
SI unit: In system international its unit is “ kg/m^3 .
Sub Units: Its sub-units are “g/cm^3 “ mg/mm^3
How to find density practically:
Practically density of an object can be find by different procedures like by method of measuring cylinder and spring balance . It is the simplest method with the help of which we can find density of any object easily.
Objects are of two classes:
> Regular objects or Geometrical objects
> Irregular objects or Non- Geometrical objects
Regular objects: Regular objects are those objects whose shapes are defined means an object who has a geometrical shape like square, circular, spherical, rectangular, triangular, cubical, parallelepiped etc. Such objects are called regular objects. The densities of such objects are easy to find , Because it can be calculated through a specific mathematical formula , just we need to find mass and volume and then by putting the values finally we get the exact value of density of regular object.
Now the question is that how to find density of an irregular object or non geometrical object. Its very simple not difficult to find, we will try to make it much easy for you.
Irregular Objects: Irregular objects or non geometrical objects are those objects whose shapes are not defined means an object whose shape is not geometrical not like square nor other geometrical objects like rectangular or triangular or spherical or cubical . But it is just like a pebble or zigzag shape. Now how to find its density see the procedure below.
Procedure: Take a spring balance and a volume measuring cylinder. Spring balance is used to find mass of an object while measuring cylinder is used to find volume of an object.
Example:
Fill water in the measuring cylinder up to some reading let the water level is at 40 cm^3 which will be the initial volume “ V1 “ now drop a pebble in the water , you will see the water will rise up in the cylinder let the water level stop at 60 cm^3 which will be the final volume “ V2” now find the difference.
Change in volume = ΔV = V2 -V1
Change in volume = Δ V = 60 cm^3 - 40 cm^3 = 20 cm^3
Therefore , the volume of pebble is 20 cm^3, We proceed towards mass of the object , to find mass of that pebble take a spring balance hung the pebble in it and then note the reading on the scale.
Let the reading is 7 on the measuring scale. Now put this value in the weight formula which is given by
W = mg
7 = m ( 9.8 )
Or 7/9.8 = m
This implies that mass of an object is 0.71g .
Now we proceed towards the density of pebble by putting the values in the basic formula
D = m/v
D = 0.71g/20cm^3
D = 0.035g/cm^3 will be the required density of the pebble having an irregular shape and that's the whole procedure for non- Geometrical objects.
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