# Units, Conversions, and Physical Constants

## Units

 Unit Abbreviation Unit Name Quantity Base Units m Meter Length m kg Kilogram Mass kg Pa Pascal Pressure kg / (ms$$^2$$) s Second Time s N Newton Force kgm / s$$^2$$ K Kelvin Temperature K Hz Hertz Frequency 1 / s rad Radian Angle 1 J Joule Energy kgm$$^2$$ / s$$^2$$ W Watt Power kgm$$^2$$ / s$$^3$$ AU or au Astronomical Unit Length See Conversions

## Common Conversions

1m = 39.37 in = 3.281 ft = 1.094 yd

1 rad = 57.30$$^\circ$$

1$$^\circ$$ = 0.01745 rad = $$\pi$$ / 180

1 Pa = 9.869 x 10$$^{-6}$$ atm

1 kg/m$$^3$$ = 1000 g/cm$$^3$$

1 AU = 1.495 x 10$$^{8}$$ km = 1.495 x 10$$^{11}$$ km

1 year (yr) = 3.15 x 10$$^{7}$$ s

1 million years (my or myr) =  3.15 x 10$$^{13}$$ s

1 day = 86,400 s

1 hour = 3600 s

1 K = -273.15 C = -457.87 F

## Physical Constants

 Name Symbol Value Acceleration due to Gravity g 9.81 m/s$$^2$$ Universal Gravitational Constant G 6.674 x 10$$^{-11}$$ Nm$$^2$$/(kg$$^2$$) Speed of Light c 2.98 x 10$$^{8}$$ m/s Mass of the Sun M$$_{sun}$$ 1.98 x 10$$^{30}$$ kg Radius of the Sun R$$_{sun}$$ 695700 km

*For Planet and Moon Information see the Other Section

## Other

Guide to Greek Letters: Greek Alphabet

Power of 10 Prefixes (ex. kilo-):  Metric Prefixes

Planetary Physical and Orbital Constants: Planets and Pluto Physical Characteristics

Selected Moon Planetary and Orbital Constants: Moon Physical Data Note: To get M by itself, just divide the GM number by the Gravitational Constant G

Common Formulas, Trigonometric Identities, Derivatives, and Integrals: Mathematical Formulas