Physics Key words

Units
Pressure – Bar
Energy / Work – Joule
Power – Watt

Farad is the unit of capacitance

Henry is the unit of inductance

Coulomb is the unit of Electric charge

The SI unit of electrical resistance is the ohm (Ω)

Siemens is the unit of Electrical resistance and conductance

The maximum frictional force, when a body just begins to slide is called Limiting friction



Factor of safety
The ratio of ultimate stress to the working stress


Poisson's ratio
The ratio of Lateral strain to linear strain


Bulk modulus
The ratio between direct stress and volumetric strain


Modulus of Rigidity
The ratio of shear stress to the displacement per unit sample length (shear strain)


Young’s modulus
Young’s modulus (Y) is the ratio of the tensile/compressive stress (σ) to the longitudinal strain (ε).

✓ Compressive stress is formed when the section is subjected to axial pushes

Material	Young’s modulus	Elastic Limit	Tensile Strength
	Y (10^9 N/m²)	(10^7 N/m²)	(10^7 N/m²)
Aluminum	70	18	20
Copper	120	20	40
Wrought Iron	190	17	33
Steel	200	30	50
Bone
Tensile	16		12
Compressive	9		12

✓ A cantilever beam having uniformly distributed load on the entire length, then the maximum bending moment will be at the fixed end

When one of the links of a kinematic chain is fixed, then the chain is called mechanism

 

Radiation is the process of heat transfer from hot body to cold body without effecting the medium.

Conduction is the process by which heat or electricity is directly transmitted through the material of a substance when there is a difference of temperature or of electrical potential between adjoining regions, without movement of the material.

Convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat.

Density is the mass per unit volume.

Relative density, or specific gravity, is the ratio of the density of a substance to the density of a given reference material.

Velocity = Displacement/Time (V=D/t)

Velocity is a vector expression of the displacement that an object or particle undergoes with respect to time (m/s)

Weight is the measure of the intensity of the force imposed on the object by the local gravitational field.

Mass is a measure of the amount of matter in an object.

Specific weight (also known as the unit weight) is the weight per unit volume of a material.

Specific volume is defined as the volume per unit mass.

Pressure at a point is the force per unit area

The viscosity of a fluid is a measure of its resistance to deformation at a given rate.

Momentum of a body is given by Mass x Velocity

1 Metric horse power   =   736 watts

1 Mechanical horse power  =   746 watts

Hooke’s law

Hooke’s law states that for material loaded within elastic limits, the stress is proportional to strain, produced by stress.

Fleming's law

Pascal's law

Pressure at a point in a fluid is equal in all directions


Planck's law

Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given

temperature (T), when there is no net flow of matter or energy between the body and its environment.







Bernoulli's principle

Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy.

Working of orifice meter is based on Bernoulli's theorem

A sprayer make use of Bernoulli's theorem


Archimedes' principle

Archimedes' principle the buoyant force is equal to the weight of the displaced water