Specific Gravity - Definition, Application, FAQs

Introduction
Specific Gravity is the part that comes under Some Mechanical Properties of Matter in the subject of Physics. In this chapter, we will study Specific Gravity, Specific gravity of air, Specific Gravity of water, Specific Gravity of steel, Specific Gravity of Petrol. We will also study about Density and its effect on Specific Gravity and try to understand the term Specific Weight and its Unit. In the last section, we will learn about the density of Iron and Specific Gravity bottles.

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This Story also Contains

1. What is meant by Specific Gravity?/ What is specific gravity?
2. Specific gravity definition/ specific gravity meaning
3. SI Unit of Specific Gravity
4. Application of Specific Gravity

NOTE: Sometimes we confuse the term Relative Density and Specific Gravity. We should always remember that both these terms have the same meaning.

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What is meant by Specific Gravity?/ What is specific gravity?

We will try to understand the concept of Specific Gravity by an example :

One Sunday morning our family member planned a visit to the pool site and for this they were accompanied with rubber tubes. Initially I got confused with the idea of carrying rubber tubes along with them and wondered : How is this thing going to help me swim?. It was like a miracle for me. I didn't sink , I floated . The answer to this miracle was Specific Gravity.

Specific gravity definition/ specific gravity meaning

The term “ Specific Gravity” means weight or density of liquid compared to density of equal volume of water at standard temperature. Sometimes this term is also called Relative Density.

OR

The specific gravity formula is given below.

Specific Gravity= Density of object/Density of Water

Density, it is Physical properties of any substance referring to mass distribution over its total volume. It helps in calculating Specific Gravity.

Density = Mass/Volume

Specific Gravity= Mass of object/Mass of Water

SI Unit of Specific Gravity

As we have seen above in the formula of Specific Gravity , there is the same quantity in the numerator and denominator, so the same unit cancels each other and thus the SI unit of Specific Gravity is not defined or there is no SI unit.

Application of Specific Gravity

• Buoyancy

The main application of Specific Gravity is that it decides whether the object will sink or not.

NOTE: If the value of the Specific Gravity comes to be greater than 1 , then the object will sink otherwise it will float.

• Distinguish Physical Properties of matter

Since Specific Gravity is physical properties of matter, it helps in:

1. Mixing two or more quantities
2. Distinguish two or more minerals

Specific Gravity of Water

Specific gravity of water is taken as standard value (as it comes to 1) for calculating the Specific gravity of other matter.

NOTE: We calculate Relative Density of matter with respect to density of water calculated at 4◦c and at atmospheric pressure

Specific Gravity of air

In general , Specific Gravity of gas means density of gas with respect to density of water.

Experimentally , Specific Gravity of air equals 0.0013

Formula used: Specific Gravity= Density of object/Density of water

Since, density of air equals 1.3kg per meter cube.

Specific Gravity of Steel

We can calculate Specific Gravity of steel by the help of the above mentioned formula , Since density of different Steel comes to have Different value. Hence it is expected to experience change in Specific Gravity also .

Specific Gravity of Petrol

In case of Fuel, Specific Gravity is given by dividing the density of fuel by density of water

NOTE: We always take units of density in Pounds per Gallon

Also Read:

• NCERT solutions for Class 11 Physics Chapter 10 Mechanical Properties of Fluids
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Specific gravity of soil

The specific gravity of soil is between 2.65-2.85.

Specific gravity of sand

The specific gravity of sand is between 2.65-2.67.

Specific weight

This term generally comes in Fluid Mechanics. In Fluid Mechanics, Specific Weight means Force exerted by the gravity on unit volume of the fluid. In general it is the product of the density of the material and gravitational constant .

Or it can be written as:

?=?g

Its SI unit comes to be Newton per meter cube

Application of Specific weight

• It has wide application in soil mechanics as well as in Rock mechanics to determine the maximum stress/load a unit matter can sustain.
• It also has a prominent role in Civil Engineering or Mechanical Engineering in determining the tensile strength of mega structures.

Specific Gravity Bottle

Introduction

It is generally constructed from glass for having a clear view of the fluid content inside with a nozzle above to maintain a constant pressure .

Working principle

This apparatus is used to measure Specific Gravity of different fluid by measuring the difference in weight of filled and empty bottle and dividing it with equal volume of water

Formula Used

Sp. Gravity (fluid) = ∆W/Volume of Water

Limitation

A nozzle is fitted on the mouth of the apparatus for the aid of evaporation but it could alter the result because of its weight.

Why is the Specific Gravity test done?

• In the medical field: It is done to study the functioning of the kidney, as kidney dilutes Urine. Urine Specific Gravity test compares density of urine to density of water
• To study Porosity: Specific Gravity test is done on soil to study porosity of soil or to find void percentage and thus calculate saturation factor.

Also check-

• NCERT Exemplar Class 11th Physics Solutions
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NCERT Physics Notes:

• NCERT Notes Class 11th Physics
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