System International (SI system of units)In earlier days , many systems of units were followed to measure physical quantities. The British system of foot-pound-second or fps system, the Gaussian system of centimeter-gram-second - cgs system , the metre-kilogram-second or the mks system were the three systems commonly followed.
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To bring one common system all round the world, the General Conference on Weights and Measures in the year 1960, accepted the SI system of units. This system is a modification over mks system and is therefore written as mksA( metre kilogram second ampere) system.This uniformity was very essential to obtain the units of all the physical quantities in physics.We will find the si units for velocity using the fundamental quantities of SI system.
SI unit for velocity:In the SI system of units there are seven fundamental quantities and two supplementary quantities:Physical quantityUnitSymbolFundamental quantities:LengthmetremMasskilogramkgTimesecondsElectric currentampereATemperaturekelvinKLuminous intensitycandelacdAmount of substancemolemol
Supplementary quantities:Plane angleradianradSolid anglesteradiansrLength is defined as the distance between two points and the SI unit of length is 1 metre.Velocity is defined as the change in displacement of a body with respect to time taken for that change.Written as `nu = (dx)/dt` where dx is the change in displacement.Displacement is the distance travelled by a body in a particular direction.Displacement is equal to length , and length in SI units is measured in metres and written in symbol as m.
Time is measured in seconds.Velocity is a derived quantity using the fundamental quantities of length and time.Velocity = `("Change in displacement")/("Time taken ")` = `(metre)/(sec)`SI unit for velocity is m/s or m s-1 read as metre per second.