Physical quantities
Physical quantities can be classified by:
1 ) The type of quantity in terms of magnitude and direction 2 ) in terms of the units used
Determine the base units of pressure
Pa= kg m^-1 s^-2
What could be a reason of having a numerically incorrect equation that is homogeneous
A missing constant number. The 1/2 in the kinetic equation does not effect the unit, but it is still incorrect.
A homogeneous equation
An equation that has the same units dimensions for both sides
Physical quantities that are divided interms of their unit are either
Base quantities and derived quantities
What are the conditions of accepting a physical equation
It must be numerically correct It must be homogenous
Name the seven base quantities and state their units
Length →m Time → s Mass → kg Current →A Temperature → K Amount of substance → mol Light intensity → c
Derived quantities
Quantities that are derived from other quantities and can be defined by word equations
Scaler
Quantities that are fully described by their magnitude
vector quantity
Quantity which is described by its magnitude and direction
Base quantities
Seven primary quantities which do not require other quantities to define them, they are considered to be the base that composes all other quantities in physics
What is meant by "an equation is homogeneous with respect to its units "?
That the equation, if expressed by its base units, is the same when compared to a different equation used to calculate the same quantity if expressed by its base units
The mole
The amount of a substance in grams, which has the same number of particles present in in 12 g of c-12
The ampere
The constant current which, if maintained in 2 straight parallel conductors of infinite length, and of negligible circular cross-section, and placed 1m apart in vacuum would produce a force enbetween the two wires equal to 0.0000002 newtons per unit meter of length ( two times ten to the power negative 7)
Second
The duration of 919 2631770 periods of the radiation corresponding to the transition between the 2 hyperfine levels of the ground state of ceasium- 133
Metre
The length travelled by an electromagnetic wave in vacuum in approximately 1/ 300000000 of a second in vacuum
The kilogram is...
The unit of mass; it is equal to the mass of the International prototype kilogram
The kelvin
The unit of the thermodynamic temperature, is the fraction of approximately 1/273 of the thermodynamic temperature of the triple point of water
Base units
Units for base quantities that are defined without reference to any other units
Derived units
Units for derived quantities that are defined with reference to the base quantities