I have encounter similar problems like this on my worksheet. I just can't set up the formula for the life of me, can someone explain this to me so I can finish my homework?

 If a planet was located approximately 29 thousand light-years from the center of a galaxy and orbits that center once every 290 million years, how fast is the planet travelling around the galaxy in km/hr? If needed, use 3.0 × 108 m/s for the speed of light.

Guest Mar 20, 2017

1+0 Answers


The velocity is circumference/period.


circumference = 2pi*r  where r is radius 


r = 29000yr*365days/yr*24hr/day*3*108*m/sec*3600secs/hr*0.001km/m ≈ 2.744*1017km


period = 290*106yr*365days/yr*24hr/day ≈ 2.54*1012hr


velocity ≈ 2*pi*2.744*1017/(2.54*1012) km/hr ≈ 6.8*105 km/hr


Alan  Mar 20, 2017

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