Density

Physics-helper

  Subject :- Density

Hello guys

Am Kolapo one of the admin @Physics-helper


And am sure at the end of this lesson you should be able to know more about Density


The density of a substance is defined as the mass of the substance per unit volume


Which can be expressed mathematically as :- D=M/V

Where D= Density
            M=Mass
            V=Volume

      Determination of Density Of A Solid


1) Regular shaped solid :-
       The mass a regular shaped solid is obtained with the aid of a chemical balance. It's volume is calculated from the measurement made by using either the Vernier calipers or a micrometer screw guage depending on size and shape of the solid.

The density can be obtained by using the formula D=m/v

2) Irregular shaped solid :-   
 The volume of an irregular shaped solid is found by displacement method

Relative Density

The relative density of a substance is defined as the ratio of the mass of a given substance to the mass of an equal volume of water


R.d = mass of substance/mass of an equal volume of water

    = density of "           "/density "                      "

    = weight of "          "/weight "                  "




Note :- Relative density has no unit

Density of water = 1000kg/m³ or 1g/cm³

Density of mercury = 13.6×10³kg/m³ or 13.6g/cm³

Density or kerosene = 8.0×10²kg/m³ or 0.8g/cm³

It's kinda essential to know the density of water offhand



Now let's move to
         Uptrust

Uptrust is related to density

Uptrust is the reaction force exerted on a body when wholly or partially immersed in a liquid. It is the uptrust of sea🌊 water💧that enables the ship🚢 going and fully loaded cano🚣 to floa🕴️on the river

Uptrust =weight in air - weight in water


In conclusion the uptrust on an object🎟️ immersed in water🌊 is equal↔ to the weight of the water displaced


Archimedes Principle
States that :-
If a body is partially or fully immersed in liquid it experience an upward force (uptrust) which is equal to the weight of the fluid displaced


In essence :- Uptrust= weight of fluid displaced


Since a body that is totally immersed displaced it's volume of fluid,then the weight of displaced fluid= density of fluid × volume of fluid × acceleration due to gravity (g)

Mathematically:- Uptrust=dvg



Principle of floatation

The principle of floatation states that when a body is totally or partially immersed in a fluid, its weight is equal to the weight of the fluid.

It's similar to Archimedes Principle but the difference is just that there's nothing like upward in principle of floatation.


Hydrometers

Is an instrument used to determine the density or relative density of a liquid.


It is based on the principle of floatation


Types of hydrometers

-- Simple hydrometer

-- Practical hydrometer


Some formula you need to know under relative density 



R.d of liquid = w-w1/w-w2

Where :- w=weight of solid in air
 w1=Apparent weight in liquid
w2=Apparent weight when the object is completely immersed in water

R.d of liquid = uptrust in oil/uptrust in water




Let's solve some problems

1) An object is 9.0N in air,7.0N totally immersed in water and 7.4 totally immersed in oil (i) calculate the uptrust in water (ii) uptrust in oil (iii) R.d of oil (iv) the mass of the water displaced


2) Cold pilot volume 600cm³ has density of 0.9gcm³ when heated,the density of the oil decreases to 0.6gcm-³
The volume of the heated oil is ?


3)The pressure of gas supports 0.7m of mercury of relative density 13.3,the height of a water column which the gas will support is ?


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