Can anyone answer this question in physics below? I posted it there because it was a bit too long. Thnx?

Question

The sun revolves around the center of the galaxy with a radius of 2.2 x 10 (with the exponent of 20)m. The period of one rotation is 2.5 x 108 years. Find the mass of the galaxy.

Answer 1

we know, centripetal force holding the sun in the orbit F = mv^2/r, where m is mass of sun.
Also, since time period (T) is given, we can say it revolves 2*pi*r distance in the time period.

so, v=2*pi*r/T

hence F = m * 4 * pi^2 *r^2/T^2 (just substitute for v in F=mv^2/r)

now this centripetal force is provided by gravitation.

so, F = G * m*M /r^2 ; M--> mass of galaxy; G--> Gravitational Const

hence, G * m * M/r^2 = m *4 * pi^2 *r^2/T^2 ...(substitute for F ..)

now m cancells out and we get mass of galaxy, M

M = (4*pi^2*r^3) / (G*T^2) = please use a calculator and find out...

Answer 2

Thank u for putting such a original thinking ever any body (limited to my knowledge) put on website .When u have derived so much calculation by u r effort, why not take the rest to get answer and be immortal in the history of discovery

Answer 3

I think this will give you the right answer;

mass = (radius)cubed
(period)squared

so, the mass would be equal to (2.2x10^20)cubed divided by (2.5x108)squared.


not 100% sure of this though :)

Answer 4

Need more info on mass of sun.

Answer 5

please give the angular velocity