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**+1 **

The velocity is circumference/period.

circumference = 2pi*r where r is radius

r = 29000yr*365days/yr*24hr/day*3*10^{8}*m/sec*3600secs/hr*0.001km/m ≈ 2.744*10^{17}km

period = 290*10^{6}yr*365days/yr*24hr/day ≈ 2.54*10^{12}hr

velocity ≈ 2*pi*2.744*10^{17}/(2.54*10^{12}) km/hr ≈ 6.8*10^{5} km/hr

.

Alan
Mar 20, 2017