## 13 April 2010

### Units

Anytime when we solve physics problems we need to use all the variables in the same system of units.
It is more convenien to use International System of Units (SI units).

When you solve physics problems: remember to check the units before you substitute all the numbers into the equations.
All variables should be in SI units.
International System of Units (SI):
 Base Units length meter (m) mass kilogram (kg) time second (s) electric current ampere (A) temperature kelvin (K)
 Other Units velocity meter per second, m/s acceleration meter per second squared, force newton, pressure pascal, energy joule, power watt, electric charge coulomb, electric potential volt, capacitance farad, electic resistance ohm, inductance henry,

## Unit Conversion

 1 mile = 1609.344 meter (m) 1 meter (m) = 0.0006214 mile 1 inch (in) = 0.0254 meter (m) 1 meter (m) = 39.37 inch (in) 1 foot (ft) = 12 inch (in) 1 inch = 0.083 foot (ft) 1 foot (ft) = 0.3048 meter (m) 1 meter (m) = 3.28 foot (ft) 1 meter/second (m/s) = .................3.6 kilometer/hour (km/h) 1 kilometer/hour (km/h) = ................0.2778 meter/second (m/s) 1 mile/hour (mph) = ..........................0.447 meter/second (m/s) 1 meter/second (m/s) = .............2.24 mile/hour (mph) 1 kilogram (kg) = 2.2046 pound (lb) 1 pound (lb) = 0.4536 kilogram (kg) Temperature T (Kelvin) = T (Celsius) + 272.15 T (Celsius) = T (Kelvin) - 272.15 T (Celsius) = (5/9)* [ T (Fahrenheit) - 32 ] T (Fahrenheit) = (9/5)* T (Celsius) + 32