physicalworld(pant sir notes)

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What is science?

Organized knowledge: a systematic attempt to understand natural phenomena and use that knowledge to predict, modify, and control phenomena.

What are the steps of the scientific method?

Observation; controlled experiments; qualitative and quantitative reasoning; mathematical modeling; prediction; verification or falsification of theories.

Is there a final theory or unquestioned authority in science?

No. Theories can be modified or replaced when new observations cannot be explained.

What are the three broad branches of natural science?

Physics, chemistry, and biology.

What is physics?

The study of the basic laws of nature and their manifestations in different phenomena.

What are the two principal thrusts in physics?

Unification and reductionism.

What is unification in physics?

Explaining different natural phenomena using one or a minimum number of laws.

What is reductionism?

Understanding a complex system from the properties of its simpler constituents.

What is the macroscopic domain?

Phenomena at laboratory, terrestrial, and astronomical scales.

What is the microscopic domain?

Atomic, molecular, and nuclear phenomena.

What is mesoscopic physics?

The study of systems involving groups of roughly hundreds of atoms, between microscopic and macroscopic scales.

What size range does physics address?

From about 10^25 m, the universe scale, down to about 10^-14 m, the nuclear scale.

What are the four fundamental forces?

Gravitational, electromagnetic, strong nuclear, and weak nuclear forces.

What are the properties of gravitational force?

It arises from mass, is always attractive, acts on all objects, has infinite range, and is very weak compared with the strong nuclear force.

What are the properties of electromagnetic force?

It arises from stationary or moving electric charges, may attract or repel, acts on charged particles, and has infinite range.

What are the properties of strong nuclear force?

It acts between nucleons, may attract or repel, has a range of about 10^-15 m, and is the strongest force.

What are the properties of weak nuclear force?

It acts within elementary particles, appears in beta decay, has a range near 10^-15 m, and is much weaker than the strong nuclear force.

What quantities are conserved in physics?

Mechanical energy, total energy, mass-energy, linear momentum, angular momentum of an isolated system, electric charge, baryon number, and lepton number.

What does E = mc^2 express?

Mass-energy equivalence: mass can convert to energy and energy can convert to mass.

What is meant by symmetry of space and time?

The laws of nature do not change when the location or time of an experiment changes.

What technology follows from electromagnetic induction?

Electricity generation.

What technology follows from thermodynamic laws?

Steam, petrol, and diesel engines.

What technology follows from electromagnetic-wave propagation?

Radio, television, and phones.

What technology follows from nuclear chain reactions?

Nuclear power reactors.

What technology follows from Newton’s second and third laws?

Rocket propulsion.

What technology follows from Bernoulli’s theorem?

Aeroplanes.

What technology follows from population inversion?

Lasers.

What technology follows from X-rays?

Medical diagnosis.

What is a physical quantity?

A measurable quantity used to describe physical happenings and express physical laws.

Why is measurement necessary?

To determine magnitude, compare similar quantities, and test physical laws and equations.

How is a physical quantity represented?

Q = n × u, where n is the numerical value and u is the unit.

How do numerical value and unit vary for a fixed quantity?

They are inversely proportional: if the unit increases, the numerical value decreases.

What is a ratio quantity?

A ratio of two similar quantities, normally having only a numerical value and no unit.

What are examples of ratio quantities?

Relative density, refractive index, and strain.

What is the angle exception to ratio quantities?

Although angle is arc/radius, it is specified with degrees or radians.

What is a scalar?

A physical quantity described by magnitude only.

What are examples of scalars?

Length, time, work, and energy.

Does a negative scalar indicate direction?

No. A negative sign indicates a negative numerical value, not direction.

What is a vector?

A physical quantity having both magnitude and direction.

What are examples of vectors?

Displacement, velocity, acceleration, and force.

What is a tensor?

A quantity that behaves neither as a scalar nor as a vector; moment of inertia is an example.

What are fundamental quantities?

Independent base quantities that do not require other physical quantities for their definitions.

What are derived quantities?

Quantities obtained by multiplying or dividing powers of fundamental quantities.

Which quantities are conventionally fundamental in mechanics?

Length, mass, and time.

What is a fundamental unit?

A unit chosen for a fundamental quantity.

What is a derived unit?

A unit expressible in terms of fundamental units.

What is a system of units?

A complete set of fundamental and derived units.

What are the CGS fundamental units?

Centimetre, gram, and second.

What are the MKS fundamental units?

Metre, kilogram, and second.

What are the FPS fundamental units?

Foot, pound, and second.

What does SI stand for?

International System of Units.

What are the seven SI base quantities and units?

Length–metre; mass–kilogram; time–second; electric current–ampere; temperature–kelvin; amount of substance–mole; luminous intensity–candela.

What are the SI supplementary angle units?

Radian for plane angle and steradian for solid angle.

What is a practical unit?

A frequently used unit that may be fundamental or derived and may or may not belong to a formal unit system.

What are the SI prefixes from 10^18 to 10^3?

Exa, peta, tera, giga, mega, and kilo.

What are the SI prefixes from 10^2 to 10^1?

Hecto and deca.

What are the SI prefixes from 10^-1 to 10^-6?

Deci, centi, milli, and micro.

What are the SI prefixes from 10^-9 to 10^-18?

Nano, pico, femto, and atto.

How is the metre defined?

As the distance light travels in vacuum during 1/299,792,458 of a second.

What was the atomic standard of length?

The wavelength-based definition using krypton-86 orange-red radiation.

How was the kilogram defined in the document?

As the mass of a platinum–iridium cylinder kept at the International Bureau of Weights and Measures.

How is the second defined?

As the duration of 9,192,631,770 periods of radiation from a hyperfine transition in cesium-133.

What is a fermi?

10^-15 m.

What is an X-ray unit?

10^-13 m.

What is an ångström?

10^-10 m.

What is a micron?

10^-6 m.

What is an astronomical unit?

Approximately 1.5 × 10^11 m.

What is a light-year?

Approximately 9.46 × 10^15 m.

What is a parsec?

3.26 light-years.

What is a metric tonne?

1000 kg.

What is a quintal?

100 kg.

What is an atomic mass unit?

Approximately 1.67 × 10^-27 kg.

What is a lunar month?

Approximately 27.3 days.

What is the relation between a solar year and average solar days?

1 solar year = 365.25 average solar days.

What is the relation between a solar year and sidereal days?

1 solar year = 366.25 sidereal days.

What is a shake?

10^-8 seconds.

What is a sidereal day?

The time Earth takes to rotate once relative to a distant star.

What are dimensions?

The powers to which fundamental quantities must be raised to express a derived quantity.

What is a dimensional equation?

An equation expressing a physical quantity in terms of fundamental dimensions.

What is a dimensional formula?

The right-hand dimensional expression alone.

What is the dimensional formula of velocity?

[M^0 L T^-1].

What is the dimensional formula of acceleration?

[M^0 L T^-2].

What is the dimensional formula of momentum?

[M L T^-1].

What is the dimensional formula of impulse?

[M L T^-1].

What is the dimensional formula of force?

[M L T^-2].

What is the dimensional formula of pressure?

[M L^-1 T^-2].

What is the dimensional formula of energy?

[M L^2 T^-2].

What is the dimensional formula of power?

[M L^2 T^-3].

What is the dimensional formula of density?

[M L^-3].

What is the dimensional formula of angular velocity?

[T^-1].

What is the dimensional formula of moment of inertia?

[M L^2].

What is the dimensional formula of angular momentum?

[M L^2 T^-1].

What is the dimensional formula of gravitational constant G?

[M^-1 L^3 T^-2].

What is the dimensional formula of gravitational potential?

[L^2 T^-2].

What is the dimensional formula of surface tension?

[M T^-2].

What is the dimensional formula of coefficient of viscosity?

[M L^-1 T^-1].

What is the dimensional formula of strain?

[M^0 L^0 T^0].

What is the dimensional formula of frequency?

[T^-1].

What is the dimensional formula of heat?

[M L^2 T^-2].