**General Awareness (GA)** is the most scoring section of SSC CGL Tier I Exam. You need no formula, no rules to solve GA section. Where you can hardly solve 50-60% of the English, Quant & Reasoning Section, you can easily solve 80-90% of the GA section during the actual exam and improve your aggregate. To score high in this section, all you need to do is stay updated. And if you prepare this section diligently and tackle the questions wisely you can lock high score easily. Here are some tips and strategies for **How to Prepare General Awareness for SSC CGL 2020**. Also, you will get to know about various topics from which questions can be asked.

**General Science** is a very important part of SSC, UPSC, Bank, Railway, Police etc. different competitive exams so SSC NOTES PDF today we share **Physics Notes for Competitive Exams****.**

The International System of Units (SI), commonly known as the metric system, is the international standard for measurement.

The SI is made up of 7 base units that define the 22 derived units with special names and symbols. The SI plays an essential role in international commerce and is commonly used in scientific and technological research and development.

The international system of units was introduced to the public in 1960 as a result to earlier research that began in 1948. SI is based on the meter-kilogram second system of units (MKS).

### International System of units

The International System of units based on seven base unitsis at present internationally acceptedunit system and is widely used throughout the world. In computing any physical quantity the units for derived quantities involved in the relationships are treated as though they were algebraic quantities till the desired units are obtained

**CGS System**In this system, the unit of length is centimetre, the unit of mass is gram and the unit of time is second.**FPS System**In this system, the unit of length is foot, the unit of mass is pound and the unit of time is second.**MKS System**In this system, the unit of length is metre, the unit of mass is kilogram and the unit of time is second.**SI System**This system contain seven fundamental units and two supplementary fundamental units. The SI units are used in all physical measurements, for both the base quantitiesand the derived quantities obtained from them. Certain derived units are expressed by means of SI units of special names such as joule, newton, watt etc.

Below is the international system of units.

#### Base Units

Amount | Unit name | Unit symbol | Definition |

Length | Meter | m | The distance traveled by light in a vacuum in 1/299792458 second. |

Weight | Kilogram | kg | This is the unit for weight. The mass of the international prototype kilogram. |

Time | Second | s | The duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. |

Current | Ampere | A | The constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 m apart in vacuum, would produce between these conductors a force equal to 2×10-7 newtons per meter of length. |

Thermodynamic temperature | Kelvin | K | 1/273.16 of the thermodynamic temperature of the triple point of water. |

Substance amount | Mole | mol | The amount of substance of a system that contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12. (Limited to objects with clarified composition.) Elementary entities are subatomic particles that compose matter and energy. |

Luminosity | Candela | cd | The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. |

#### Supplementary Units

Amount | Unit name | Unit symbol | Definition |

Plane angle | Radian | rad | Radian describes the plane angle subtended by an arc of a circle with the same length as the radius of that circle corresponds to an angle of 1 radian. |

Solid angle | Steradian | sr | A steradian is a solid angle at the center of a sphere subtending a section on the surface equal in area to the square of the radius of the sphere. |

#### Derived Units

Derived units are a combination of base units and supplementary units and the mathematical symbols of multiplication and division.

Amount | Unit name | Unit symbol |

Area | Square meter | m^{2} |

Volume | Cubic meter | m^{3} |

Speed | Meter per second | m/s |

Acceleration | Meter per second squared | m/s^{2} |

Wavenumber | Reciprocal meter | m^{-1} |

Density | Kilogram per cubic meter | kg/m^{3} |

Current density | Ampere per square meter | A/m^{2} |

Magnetic field strength | Ampere per meter | A/m |

Concentration (of amount of substance) | Mole per cubic meter | mol/m^{3} |

Specific volume | Cubic meter per kilogram | m^{3}/kg |

Luminance | Candela per square meter | cd/m^{2} |

Some derived units are given unique names.

Amount | Unit name | Unit symbol | Composition |

Frequency | Hertz | Hz | 1Hz=1s^{-1} |

Force | Newton | N | 1N=1kg･m/s^{2} |

Pressure, stress | Pascal | Pa | 1Pa=1N/m^{2} |

Energy, work, amount of heat | Joule | J | 1J=1N･m |

Power, radiant flux | Watt | W | W=1J/s |

Electric charge, amount of electricity | Coulomb | C | 1C=1A･s |

Electric potential/electric potential difference, voltage, electromotive force | Volt | V | 1V=1J/C |

Resistance (electrical) | Ohm | Ω | 1Ω=1V/A |

Conductance (electrical) | Siemens | S | 1S=1Ω^{-1} |

Magnetic | Weber | Wb | 1Wb=1V･s |

Magnetic flux density, magnetic induction | Tesla | T | 1T=1Wb/m^{2} |

Inductance | Henry | H | 1H=1Wb/A |

Celsius temperature | Degree Celsius | ℃ | 1t=T-To |

Luminous flux | Lumen | lm | 1lm=1cd･sr |

Illuminance | Lux | lx | 1lx=1lm/m^{2} |

SI unit prefixes indicating integer powers of ten

Factor | Prefix | Symbol | Factor | Prefix | Symbol |

10^{18} |
exa | E | 10^{-1} |
deci | d |

10^{15} |
peta | P | 10^{-2} |
centi | c |

10^{12} |
tera | T | 10^{-3} |
milli | m |

10^{9} |
giga | G | 10^{-6} |
micro | µ |

10^{6} |
mega | M | 10^{-9} |
nano | n |

10^{3} |
kilo | k | 10^{-12} |
pico | p |

10^{2} |
hecto | h | 10^{-15} |
femto | f |

10 | deka | da | 10^{-18} |
atto | a |

#### Non-SI units

Amount | Unit name | Unit symbol | Definition |

Time | Minute | min | 1min=60s |

Hour | h | 1h=60min | |

Day | d | 1d=24h | |

Plane angle | Degree | ° | 1°= (π/180) rad |

Minute | ′ | 1′= (1/60) ° | |

Second | ″ | 1″= (1/60) ′ | |

Volume | Liter | l, L | 1l=1dm^{3} |

Weight | Metric ton | t | 1t=10^{3}kg |