Specific Weight & Gravity - Free MCQ Practice Test with solutions, GATE

• 1 litre is equal to 1 cubic decimetre.
• That is the volume of a cube 10 centimetres × 10 centimetres × 10 centimetres.
• 1 L ≡ 1 dm³ ≡ 1000 cm³
• 1 L ≡ 0.001 m³ ≡ 1000 cm³

The hydrometer is a device which is used to measure specific gravity.
Various devices/equipment and their use is described in the table below:

The hydrometer is a device which is used to measure specific gravity.
Various devices/equipments and their use is described in the table below:

Concept:
In thermodynamics and Fluid Engineering, compressibility is a measure of the relative volume change of a fluid as a response to pressure (or mean stress) change.
Compressibility in Fluid Engineering is expressed as follows:

where, ∂p = change of pressure, ∂v = change in the volume
K = bulk modulus
(-ve) sign indicates, there is a decrease in volume due to an increase in pressure.

Calculation:
Given:
dV = 0.2%, δP = 15 - 7.5 = 7.5 MPa 

Concept:
When a body is submerged in a fluid, it undergoes hydraulic stress (equal in magnitude to the hydraulic pressure); This leads to a decrease in the volume of the body thus producing a strain called volume strain

• The ratio of hydraulic stress to the corresponding hydraulic strain is called bulk modulus
• 

Calculation:
Given:
P₁ = 50 kg/cm², P₂ = 150 kg/cm², V₁ = 0.04 m³, V₂ = 0.039 m³

= 4000 kg/cm²

Concept:
In thermodynamics and Fluid Engineering, compressibility is a measure of the relative volume change of a fluid as a response to pressure (or mean stress) change.
Compressibility in Fluid Engineering is expressed as follows:

where, ∂p = change of pressure, ∂v = change in the volume
K = bulk modulus
(-ve) sign indicates, there is a decrease in volume due to an increase in pressure.

Calculation:
Given:
β = 0.75× 10^-9 m²/N, V = 0.01 m³, dP = 2 × 10⁷ Pa
Compressibility (β)


dV = 1.5 × 10^-4

Specific Volume

• The specific volume of the fluid is defined as the volume of the fluid occupied by a unit mass or volume per unit mass of a fluid is called a specific volume.
• Specific volume is reciprocal of mass density.

Viscosity

• Viscosity – the property of the fluid which offers resistance to the movement of one layer of fluid over another layer.
• SI unit of viscosity is 
• CGS unit of viscosity also called poise 
• 1 poise =

Specific weight:

• Specific weight is defined as weight per unit volume.
• 
• Its unit is N/m³.

Specific gravity is the ratio of the specific weight of the liquid to the specific weight of a standard fluid. In the case of liquids standard fluid is taken as water with specific gravity 1.

Concept:
Specific gravity of the body is given by:

Calculation:
Given:
weight in air = 400 N, weight in water = 300 N
weight loss = 400 - 300 = 100 N
Specific gravity of marble stone is:

• The reciprocal of the mass density is known as Specific volume.
• The Specific volume of a material is the ratio of the volume of the material to its mass.
• It is both the inverse of mass and the intrinsic property of matter.
• Specific volume is defined as the number of cubic meters occupied by one kilogram of a substance.
• The normal unit shall be the cubic meter per kilogram (m3/kg)
• The specific volume for the ideal gas is also equal to the gas constant (R) multiplied by the temperature and then divided by the pressure multiplied by the molar mass of the ideal gas.

Dimensional Analysis:

• The systematic procedure of identifying the variables in physical phenomena and correlating them to form a set of the dimensionless group is known as dimensional analysis.

Specific volume:

• It is defined as the volume per unit mass.
• Thus, L³M^-1T⁰ is the dimensional formula of Specific volume.