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If a planet was located approximately 31 thousand light-years from the center of a galaxy and orbits that center once every 286 million years, how fast is the planet traveling around the galaxy in km/hr? If needed, use 3.0 × 108 m/s for the speed of light.

 Jan 17, 2021
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radius of  circle =   31000  light years

 

Number of  m  in one light year  =    3 * 10^8 / s  *  (3600 * 24 * 365)s   = 9.4608 * 10^15   m

 

Converting this to km   (divide by 10^3)  =   9.4608 * 10^12  km   in one light year

 

So   .....radius of this  circle =   31,000 * 9.4608 * 10^12 km  = 2.932848 * 10^17 km

 

Total distance  traveled by planet in one orbit =  2pi * r =   2 pi * 293.2848 * 10^17km

 

Convert  286,000,000 years  to hrs =   286,000,000  * 24 * 365  = 2.50536 * 10^12  hrs 

 

So....the speed is

 

D / T  =         [ 2pi * 293.2848*10^17] km  /  [ 2.50536 * 10^12  ]hr    ≈ 7.36 * 10^7   km/hr

 

 

 

cool cool cool

 Jan 17, 2021

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