chapter1-units and measurements

• • There are three systems of units. The British system(FPS) , the metric system(CGS and MKS) and the SI units(modified of MKS)
• The derived unit of velocity(speed) is m/s.
• The derived unit of density is kg/m3.
• The standard form of length is Metre.
• The unit of Angstrom is 1 x 10^-10 m.
• The unit of length used by particle physicists is Femtometre(fm).
• The standard of mass is a cylinder of 1 kg.
• The SI base unit of electric current is Ampere(A)
• The SI base unit of temperature is Kelvin(K)
• The SI base unit of amount of substance is mole(mol)
• The SI base unit of time is Second(S)
• A physical quantity consists of a numeral value and a unit.
• The light year is the distance light travels in a year.
• Screw gauge (Micrometer) is suitable to measure the length less than 2cm.
• Nanometer is equal to 10^-9 meter.
• Millimeter is equal to 10^-3 meter
• Centimeter is equal to 10^-2 meter
• Kilometer is equal to 10^3 meter
• Femtometer is equal to 10^-15 m.
• Picometer is equal to 10^-12 m.
• The SI unit of Luminous intensity is Candela (cd).
• The largest unit of length is parsec (pc).
• Accuracy of Vernier caliper is 0.1mm = 0.01cm.
• Accuracy of measuring tape is 1mm = 0.1cm.