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